netre, or all the molecules in a slice of 1/10,000 of the thickness of that cube. Think of a cube filled with particles, like these glass balls, scattered at random through a space equal to 1,000 times the sum of their volumes. Such a crowd may be condensed (just as air may be condensed) to 1/1,000 of its volume; but this condensation brings the molecules into contact. Something comparable with this may be imagined to be the condition of common air of ordinary density, as in our atmosphere. The diagram with size of each molecule, which, if shown in it to scale, would be 1 millimetre (or too small to be seen by you), to represent an actual diameter 1/10,000,000 of a centimetre, represents a gas in which a condensation of 1 to 10 linear, or 1 to 1,000 in bulk, would bring the molecules close together.

Now you are to imagine the particles moving in all directions, each in a straight line until it collides with another. The average length of free path is ten centimetres in our diagram, representing 1/100,000 of a centimetre in reality. And to suit the case of atmospheric air of ordinary density and at ordinary pressure, you must suppose the actual velocity of each particle to be 50,000 centimetres per second; which will make the average time from collision to collision 1/5,000,000,000 of a second.

The time is so far advanced that I cannot speak of the details of this exquisite kinetic theory, but I will just say that three points investigated by Maxwell and Clausius-viz. the viscosity, or want of perfect fluidity of gases; the diffusion of gases into one another; and the diffusion of heat through gases-all these put together give an estimate for the average length of the free path of a molecule. Then a beautiful theory of Clausius enables us from the average length of the free path to calculate the magnitude of the atom. That is what Loschmidt has done, and I, unconsciously following in his wake, have come to the same conclusion; that is, we have arrived at the absolute certainty that the dimensions of a molecule of air is something like that which I have stated.

The four lines of argument which I have now indicated, lead all to substantially the same estimate of the dimensions of molecular structure. Jointly they establish, with what we cannot but regard as a very high degree of probability, the conclusion that, in any ordinary liquid, transparent solid, or seemingly opaque solid, the mean distance between the centres of contiguous molecules is less than the 1/5,000,000, and greater than the I/1,000,000,000 of a centimetre.

To form some conception of the degree of coarsegrainedness indicated by this conclusion, imagine a globe of water or glass, as large as a football,3 to be magnified up to the size of the earth, each constituent molecule being magnified in the same proportion. The magnified structure would be more coarse-grained than a heap of small shot, but probably less coarse-grained than a heap of footballs.

were present:-The Duke of Northumberland, the Duke and Duchess of Westminster, Sir William Siemens, Sir Frederick Abel, Sir Lyon Playfair, M.P., Sir Frederick Pollock, Sir T. Spencer Wells, Mr. George Cubitt, M.P., Dr. Farquharson, M.P., Col. Makins, M.P., Capt. Galton, Mr. Edwin Chadwick, C.B., Mr. Ernest Hart, Mr. C. Waring, the Hon. Rollo Russell, General Lowry, C. B., Mr. George Shaw (chairman of the City Commission of Sewers), Mr. W. R. E. Coles, Mr. W. Chandler Roberts, of the Royal Mint, and Mr. Gregory, Master of the Clothworkers' Company.

The proceedings were opened by the reading of a Report, which has been carefully prepared by the Council, detailing the steps which have already been taken, and giving particulars of the exhibitions of last year in London and Manchester. The Report also deals with the work which has been done regarding the chemical composition of smoke by Prof. Chandler Roberts, and the many tests of coal made by Mr. Clark. In this important investigation, attention was called to the fact that a very great discrepancy exists between the heating efficiency of various types of grates, stoves, furnaces, and the like. In some forms of grate, for instance, only 22 per cent. of the total heat is utilised, whilst others require nearly three tons of coal to do the same work which other stoves manage to get out of one ton.

The Council desired to report that, so far as they had been able to ascertain, the most marked benefit resulting from the movement had been in the increased use of gas and coke for heating purposes. The improvement in gasheating apparatus had been considerable, and the use of coke had been greatly facilitated by its being supplied to the public in more convenient sizes than formerly, and by the introduction of firebrick or other slow-conducting substances used in the fireplaces for burning it. The use of smokeless coal had also been extended in the metropolis; but the Council found that the description of such coal supplied was in a large number of instances unsuitable or inferior, and from that cause, coupled with the fact that smokeless coals were not generally supplied by coal merchants, there had not been, so far, any very marked increase in its consumption. Marked improvement had, however, been made in open grates and stoves for burning that description of coal, and one firm of manufacturers, who brought out a cheap stove at the South Kensington Exhibition, had sold upwards of 14,000 during the past two years; and they reinarked that the public seemed ready to burn non-smoky coal if proper stoves for using it were offered at a reasonable price. Appliances for improving the draught of chimneys had also been introduced lately, and that tended to facilitate the use of smokeless coal. The Council had examined the present state of the administration of the law for the suppression of smoke, and they considered that in view of the enormous extension of buildings and factories in London and large towns, and in view also of the evidence that smoke could be to a great extent, if not entirely, avoided, the scope of legislative enactments for abating smoke should be extended and their provisions duly enforced.

One part of the Report deals with a matter to which we attach the greatest importance. It is suggested that there should be some place which the public can visit and where they may examine any apparatus that is approved of, or which they may wish to purchase; but above this it is pointed out that a place is requisite where scientific, chemical, and other tests may be made for the information of the public generally, but especially for the

there was secured a blue coloured glass ball of four centimetres diameter; and similarly to each cord of the other five rows, a red coloured ball of the same size. A ball from one of the outer rows was pulled aside, and, being set free, it plunged in amongst the others, causing collisions throughout the whole plane in which the suspended balls were situated.

2 Sitzungsberichte of the Vienna Academy, Oct. 12, 1865, p. 395.

3 Or say a globe of 16 centimetres diameter.

try new suggestions. The Report also suggests that in connection with this there should be some place for discussion and public lectures, for the general advancement and diffusion of knowledge touching smoke abatement. The third proposal is certainly the most doubtful one, but the

first and second are so important that the less time that is lost in starting such an institution the better; and we are glad to learn that towards its foundation the Duke of Westminster has promised 500l., Mr. C. Waring 100/., and Mr. Cubitt 100/.

The most important speech, perhaps, was that made by the Duke of Westminster, in moving the adoption of the Report. He pointed out that we are face to face with a very gigantic evil-an evil not only gigantic in itself, but, considering the enormous yearly increase of 40,000 in the population, one of a very alarming character. Therefore it was necessary that some steps should be taken to abate, if not to entirely do away with, that monstrous evil, which affected the health and vitality of the inhabitants of the metropolis. They were all aware of the evil effects of smoke, and how far worse it became when mixed with fog, but they believed that it was an evil which might be considerably modified if not entirely prevented. They had indisputable authority for saying that smoke was very wasteful and destructive. The waste in London alone amounted to one million yearly, and the waste in the country must be taken in proportion to that in the metropolis. They had also the highest authority for informing the public that the evil affected the health of those who lived under the canopy of smoke. Its effect on public buildings was also most destructive, and Mr. Shaw-Lefevre had said that to repair the damage done by its agency to the Houses of Parliament alone involved an expenditure of 2500l. per annum, and there could be no greater curse and bane to the metropolis than that smoke nuisance. The object of the meeting was to impress upon the public the importance of the subject. The Smoke Nuisance Act had been useful in the past, and could be made more efficacious in the future if its provisions were more strenuously enforced. Quoting from the correspondence which had taken place between the Home Office and the Association upon the subject, the speaker said that the Home Secretary had stated that in the majority of cases the fines inflicted were far less in amount than had been contemplated by the Act. That was not a right state of things, and efforts should be made to remedy it as soon as possible; and it was not unreasonable to suppose that with a proper enforcement of the law a check to a certain extent might be put upon the nuisance. After son.e other observations, his Grace concluded by moving the adoption of the Report.

Sir Spencer Wells and Sir Frederick Abel spoke in favour of the Duke of Westminster's proposal, which was carried unanimously.

The next resolution was moved by the Duke of Northumberland, and was to the following effect :-"That the period has now arrived at which systematic inquiry is desirable into the application of the resources of technical science for the abatement of smoke now largely produced in industrial processes and in the heating of houses, as well as into the operation of the existing laws for smoke abatement; and that the Council of the National Smoke Abatement Institution be requested to urge upon the Government the desirability of appointing a Royal Commission for the purpose."

This was seconded by Sir Wm. Siemens and carried. We are glad to see that it was acknowledged that the stated objects of the Smoke Abatement Institution, and the success which has attended its past efforts, had established a claim not only to the support of the meeting, but to that of the City of London and other great cities and towns.

We must congratulate the Council of the new institution upon the energy which they are displaying, and we believe that in a few years the success they will then have met with will lead one to hope that in process of time the smoke nuisance which kills its tens of thousands annually, and makes life in a great city like London almost unbearable, will to a certain extent be done away with.

NOTES

GREAT efforts are being made by the Council of the Society of Arts and its chairman, Sir William Siemens, who has again been elected to this office, to make their conversazione, to be held on the 25th inst. at the Fisheries Exhibition, a great success. The fountains are to be illuminated by coloured fires, and the gardens, as well as the Exhibition Buildings, will be lighted by the electric light. The band of the 6th Thuringian Regiment of German Infantry will perform in the building.

A MEETING which may have an important result upon science and art instruction in this country has been inaugurated at Manchester. An association has been established to effect the general advancement of the profession of science and art teaching by securing improvements in the schemes of study and the establishment of satisfactory relations between teachers and the Science and Art Department, the City and Guilds of London Institute, and other public authorities. It proposes also to collect such information as may be of service to teachers professionally, and it will endeavour by constant watchfulness to advance the status and material interests of science and art teachers in all directions. The president of the new Association is Prof. Huxley,

and the vice-presidents are Dr. H. E. Roscoe, Mr. Norman Lockyer, Prof. Boyd Dawkins, Prof. Gamgee, Prof. Ayrton, Prof. Silvanus Thompson, Dr. John Watts, Mr. S. LeighGregson, Mr. John Angell, Mr. W. Lockett Agnew, Mr. C. M. Foden, and Mr. J. H. Reynolds. Mr. W. E. Crowther, of the Technical School and Mechanics Institution, Manchester, is the Honorary Secretary, and all communications should be addressed to him, especially by those who are desirous of forming affiliated unions in other districts. We believe that branches are already being established at Newcastle-upon-Tyne and Liver pool.

Dr. J. H. GILBERT, F.R.S., has been elected a Correspond. ing Member of the Institute of France (Academy of Sciences).

THE treasurer of the Darwin Memorial Fund has received through Dr. Elforing of Helsingfors a cheque for 941. 45., that being the amount collected in Finland as a contribution to the memorial. That so large an amount should have been collected in so small a country is only an additional proof of the ready recognition which the great works of Darwin have received in other countries as well as our own. The fund now amounts to 33001.

THE Lick Observatory, we learn from Science, has made much progress during the past year. The dome for the small equatorial has now been finished, and is certainly the most complete and convenient one of its size in America. The building of the observatory in which the great thirty-six-inch equatorial is to be placed is also progressing. The walls of the main building are half completed, and the cellar for the dome has been excavated. The four-inch transit-house and the buildings for the photoheliographs have been in working order now for some time, as they were used in a successful observation of the transit of Venus last December. In a few weeks the building for the meridian circle will be commenced, as well as a house for the astronomers and buildings to contain the appliances for moving the dome, and for the general heating and lighting of the observatory. Two brick reservoirs for spring water, the one containing 83,000 gallons, the other 20,000 gallons, have been constructed, and another reservoir to contain 83,000 gallons of rain-water will shortly be commenced. The roads have been extended. Some of the original arrangements of the observatory buildings, which were only provisional, have now been replaced by more substantial and permanent structures, and by the end of the season great progress will have been made.

Science announces the death last month of Stephen Alexander, Professor Emeritus of Astronomy at Princetown. He was educated at Union College, where he graduated in 1824. In 1840 he was appointed Professor of Astronomy at Princetown, and more recently he received a Professorship of Mechanics. It was as an astronomer, however, that he was most generally known.

We have been asked by the local secretaries of the Meeting of the British Association for the Advancement of Science to be held at Southport in September next to call the attention of those who have in their possession scientific instruments, curiosities, and other objects of special or artistic interest, to the fact that there will be an exhibition of such articles in connection with the meeting of the Association. Intending exhibitors and others interested in this matter should communicate with Mr. Ch. de Wechmar Stoess, the Hon. Sec. Conversazione Committee, and Mr. Alfred Morgan, the Hon. Sec. for Exhibits, immediately.

THE steamer Pola has just called at Reikjavik, in Iceland, on her way to Jan Mayen, to bring away the Austrian observation party wintering there. Towards the end of the present month the Swedish gunboat Urd will proceed to Spitzbergen to relieve the Swedish party wintering there. It is reported, both from Iceland and Norway, that the state of the ice in the Arctic seas is very favourable to navigation.

THE Sophia, Baron Nordenskjöld's vessel, left Rödefjord, Iceland, for Ivigtuk, in Greenland, on June 10, leaving Count Strömfelt and Drs. Arpi and Flink behind to pursue geological and botanical researches there.

A LETTER from M. Thouard, the well-known French traveller, dated Santiago (Chili), states that he heard from Chiriguanos Indians that a part of the Crevaux party were still prisoners of the Tobas tribe. M. Thouard will try to assist his countrymen. MR. CROOKES and Professors Odling and Tidy have lately given in their Report on the composition and quality of London water during 1882 to the Local Government Board. In that year they examine 2110 samples of water drawn in nearly equal proportions from the mains of all the seven London Companies; testing generally seven samples daily by their colour according to the registers of the colour-meter, by the quantity of free oxygen and ammonia contained in them, by the amount of oxygen required for oxidation of the organic matter present in them, by their proportions of organic carbon and nitrogen, of nitrates and chlorine, and by their initial hardness in degrees of Clark's scale. The results exhaustively set forth in numerical tables are further illustrated by seven diagrams, in each of which three wave-lines represent the fluctuations throughout the year of discoloration, of the proportion of organic carbon, and of the amount of oxygen required to oxidise the organic matter of the water of the London Company in question. These diagrams show to the eye what the statistics confirm, the remarkable parallelism existing between the degree of discoloration, the amount of organic carbon present in the water as determined by combustion, and the amount of oxygen requisite to oxidation of the organic matter as determined by permanganate. The Report altogether would seem to reflect most favourably on the quality of London water. Throughout

the whole year the water of the New River Company as determined by the samples was, without exception, "clear, bright, and well filtered," a character supported by analyses of other kinds, and in only a few cases in the samples of the other Companies was the water describable as "turbid," "slightly turbid," or very slightly turbid." For the nine months from February to October 1882 the organic matter in the water of all the London Companies is estimated at 137 per 100,000, and the highest monthly mean for the same period at 181 per 100,000. There is, however, one important factor in the question with which

chemical analysis cannot directly cope, the comparative innocuousness, namely, of the organic matter present in the water accord. ing as it is of vegetable origin, or its comparative virulence according as it is of animal origin. As Prof. Huxley, in a lec ture in 1880 to the Chemical Society, said, water as regards chemical analysis may be perfectly unobjectionable, and yet as regards its operation on the human body deadly as prussic acid,

WE have received advanced copies of the following books from the Literary Superintendent of the Fisheries Exhibition :"British Marine and Freshwater Fishes," by W. Saville Kent, F. L.S., F.Z.S.; "Zoology and Food Fishes," by George Bond Howes, Demonstrator of Biology at the Normal School of Science; "On the Capture of Salmonida and the Acclimatisa tion of Fish," by Sir James Ramsay Gibson Maitland, Bart.; and "The Fishery Laws," by Frederick Pollock. We must congratulate the Commissioners of the International Fisheries Exhibition on their activity, and on their care for the scientific aspect of the specimens in their collection. There are two kinds of books published by the Exhibition authorities. Reports of papers read at the conferences and the important discussions which have followed their reading are published, and other books are written in explanation of the exhibits and other subjects bearing upon fish and fish culture.

THERE is an interesting article on "The Import Duty on Scientific Journals" in Science for June 29. The writer ventures to suggest that at its next meeting, the American Association for the Advancement of Science should appoint a committee to draw up a definite list of those foreign technical journals of mathe. matics, physics, chemistry, mineralogy, geology, geography, botany, zoology, physiology, and ethnology which do not com pete with similar enterprises of publishing firms in the United States, and urge Congress to pass a special Act putting these journals on the free list. The article goes on to say that, if a suitable Bill were drawn up, there is little doubt that some member of Congress could be found to introduce it, and if framed so that it touched no publisher's pocket, and vigorously supported by the scientific influence of the country, it would certainly become law.

THE earthquake at Voss in Norway on June 13, reported in NATURE last week (p. 233), was felt over the entire district between Bergen and Aalesund, but most severely in the wellknown Dalsfjörd. A further shock was felt over the same district on June 15 at 1.50 p.m., and some people assert that another followed at about II a.m. on the following day.

On the evening of the 2nd inst. a terrific cyclone passed over Stockholm. Its course was north-west to north-east. Houses were unroofed, trees uprooted, and a number of people thrown down, while not a shred of canvas was left on the masts of the vessels in the harbour. Barely a mile from the track of the cyclone there was almost a perfect calm.

WE learn that the Dutch Government have decided not to grant the sum of 30,000 guilders which Baron Nordenskjold claims as the discoverer of the North-East Passage. The decision is founded on the motive which led the States General in 1596 to offer this award, viz. to find a passage of commercial value to the nation; Baron Nordenskjöld having, however, dis covered what may be termed a purely scientific one, the award, it is argued, has not been earned. As several reasons have been advanced for this claim made by the gallant Swedish explorer, we do not think we err when we assert that it was his intention to have expended the sum in the interest of science, viz. on an expedition to the Arctic regions.

A STATE paper recently issued by the Minister of Public Works in France contains some interesting details on the French

mineral waters. There are 1027 sources which are worked. Of these 319 are sulphurous, 357 alkaline, 136 iron, and 215 salt; 386 are cold, that is to say, they do not exceed 15° C. in temperature, and 641 are thermal. They are distributed as follows: --Puy-de-Dôme, 94; Ardèche, 77; Vosges, 76; Ariège et Pyrénées Orientales, 69; Hautes-Pyrénées, 64. The paper also states the number of visitors to these different waters. It appears that the Hautes-Pyrénées are the most frequented. During the past year this department alone has had 44,476 visitors, thus distributed :-Puy-de-Dôme, 18,619; l'Alliers, 16,430; la HauteGaronne, 14, 230; les Landes, 12,954. The water flowing from all the 1027 sources is estimated at 46,412 litres per minute.

THE Chevalier Frédéric Franchetti, engineer at Leghorn, has referred M. de Parville to a curious passage in Galileo's "Dialogues" touching a possible early origin of the electric telegraph. In the dialogue Sagrado says that he calls to mind a man who wanted to tell him a secret which would give him the power by means of a certain sympathy of magnetised wires to speak to any one two or three thousand miles off. The bargain however fell through, as the inventor would not try any shorter distance, and Sagrado declined to go to Cairo or Muscovy to try the experi

ment.

The story is told in the last number of the Revue Scientifique. The reference given is p. 97 of the first day, Leghorn Edition, 1874.

THE Executive Committee of the International Fisheries Exhibition has published a penny plan and tour as a complete guide to the leading and most interesting features of the Exhibition, which we think will prove useful.

WE have some very interesting figures before us comparing the different modes of illumination in respect to the amount of products of combustion :

Products per hour.

1882. Besides the usual statistics, a great part of the report is occupied with suggestions for the improvement of the present law of the colony for preventing accidents to workmen in mines.

FROM a comparison between the lists of birds observed at Saltdalen in Norway by the ornithologist Sommerfelts, from 1805 to 1825, and those which are now found in the district, it would appear, according to Herr Hageman of the Norwegian Forest Department, that the smaller singing birds are much more largely represented now than formerly. The ortolan and crossbill, Hirundo urbica and rustica, the common sparrow and the chaffinch, which are now abundant, were then unknown in the district, while the common sparrow was only observed on one occasion by Sommerfelts. Herr Anda ascribes the present increase in numbers and species to the better cultivation of the land and the clearing of the fir-woods.

THE additions to the Zoological Society's Gardens during the past week include a Kinkajou (Cercoleptes caudivolvulus) from South America, presented by Mr. H. V. Brackenbury; a Syrian Fennec (Canis famelicus) from North Africa, presented by Mr. J. H. James; a Blau-bok (Cephalophus pygmæus ?) from South Africa, presented by Mr. Ernest Honey; a Slender-billed Cockatoo (Licmetis tenuirostris) from Australia, presented by Mrs. A. C. Biddle; an Earl's Weka Rail (Ocydromus carlii) from North Island, New Zealand, presented by Mrs. Wilson; two Wood Owls (Syrnium aluco), British, presented by Mr. J. Metcalfe; two Black Guillemots (Uria grylle) from Ireland, presented by Mr. H. Becher; a Vervet Monkey (Cercopithecus lalandii 8) from South Africa, a Moor Macaque (Macacus maurus 8), a Bonnet Monkey (Macacus radiatus) from India, two Common Snakes (Tropidonotus natrix, var.), European, a Spotted Cavy (Calogenys paca), two Hairy-rumped Agoutis (Dasyprocta prymnolopha) from Guiana, deposited; a Black Howler (Mycetes caraye 8) from Brazil, purchased; a Japanese Deer (Cervus sika 8), a Burrhel Wild Sheep (Ovis burrhel ?), born in the Gardens.

Lamp, petroleum, flat flame... o'80

These we think are quite sufficient to show the great supremacy of electric lighting over all other methods of illumination when considered as a matter of health.

WE learn from Naturen that a hitherto unknown form of the potato disease, which had been making slow but steady progress near Stavanger during the last ten or twelve years, has recently begun to show increased energy. The stalk of the plant is the part affected, and here Herr Anda has discovered small white fungoid growths, which after a time assume a greenish, and finally a black, colour, after attaining the size of a small bean. While the fungus is rapidly increasing at the expense of the plant, the interior of the stem is first reduced to a pulpy condition, and next shrivelled and hollowed out, until nothing remains but a mere outer shell, which breaks down on being touched. When the ripe black germs of the fungus have remained in the earth through the winter, they are found after the return of the next year's warmth to have developed small stalked fruits filled with minute spores, which penetrate into the young plants before they appear above the ground. The end of July or beginning of August is the time when the ravages of the fungus are most conspicuous, and at those periods whole fields of potato plants are often rapidly reduced to the condition of

withered straw.

WE have received from the Minister of Mines of New South Wales the report of the Chief Inspector of Mines for the year

OUR ASTRONOMICAL COLUMN

THE TOTAL SOLAR ECLIPSE OF AUGUST 28-29, 1886. — This great eclipse is a return of that of August 17-18, 1868, which was extensively observed in the Bombay and Madras Presidencies and in other parts of its track from Aden to Torres Straits. In 1886 the track of the central line is mainly over the Atlantic Ocean, and at that portion of it where the duration of totality is longest it will not be observable on land. It is therefore of interest to examine the possible conditions of observation. In deducing the results which follow, the places of the sun and moon have been taken from the Nautical Almanac, where Newcomb's corrections to Hansen's Lunar Tables are introduced. As will be seen from the Ephemeris, the central eclipse commences in longitude 79° 46′ west of Greenwich, and latitude 9° 48' north, off Colon, in the isthmus of Panama, thence running

in the direction of the Windward Islands across the northern parts of New Grenada and Venezuela; passing over the Island of Grenada, it traverses the Atlantic, and meets the coast of Benguela, and crossing South Africa to Sofala, it ends on the Africa in the Portuguese possessions, not far from St. Philip de east coast of Madagascar. At Cartagena the duration of totality is 3m. 2s., with the sun at an altitude of 5°; at Maracaybo the duration is 2m. 57s., with the sun 9° above the horizon. The southern extremity of the Island of Grenada will have the most advantageous conditions for observation, having regard begins there at 7h. 11m. to length of totality and accessibility. The total eclipse Os. a.m. on August 29, and continues 3m. 42s., the sun being at an altitude of 20°; at the northern extremity of the island the length of total eclipse is about five seconds less. In Carriacou, the principal island in the Grenadines, the duration of totality is 3m. 21s.; at the northern point of Tobago it is Im. 51s. On the Atlantic, where the sun is on the meridian at the middle of the eclipse, or in longitude 14° 27' west and latitude 2° 57′ north,

totality, according to the elements we have adopted, will continue for 6m. 31s. Near St. Philip de Benguela, on the central line, we find the sun will be hidden for 4m. 23s., but the locality will hardly attract observers. It would rather appear that we must look for observations of this eclipse to the Windward Islands only. The small island of Blanquilla is close upon the central line, but the sun has of course a less altitude there than in Grenada.

The eclipse of August 7-8, 1850, one of the same series, was observed in the Sandwich Islands, the whole track of totality lying on the Pacific.

TEMPEL'S COMET, 1873, II.-According to M. Schulhof's corrected elements of this comet's orbit, which assigned a period of revolution of 5.200 years, at the last appearance in 1878, the next perihelion passage, neglecting the effect of perturbation, which can hardly be very material during the present revolution, may take place about November 19 under circumstances that will render observations difficult if they are practicable at all. Assuming the comet to be in perihelion on November 195 G.M.T., we should have about the following positions :

SOLID AND LIQUID ILLUMINATING AGENTS THE Journal of the Society of Arts publishes in a recent

number an interesting lecture given by Mr. Leopold Field, F.C.S., on "Solid and Liquid Illuminating Agents." Mr. Field not only deals with the chemistry of these bodies, but he gives also a most interesting account of the means of lighting in use among the ancients, to which a brief reference may be made.

The earliest known method of illumination was in all proba bility that of the torch, formerly used largely in northern countries, and doubtless still furnishing the Lapp and the Finn with their light. The torch is cut from the pitch pine, and around it clings the exuded resin. When lighted it burns with a large red flame, producing a great deal of smoke. Used for cooking purposes a brand might get saturated with fat, so that it would burn longer without consuming its own fibre.

This, as pointed out by Mr. Field, was the old method of lighting. Substituting for their brand a piece of rope and saturating this with pitch or resin we get the modern link, connecting us on foggy days with the old modes of lighting. The work link itself, and probably also the idea, comes from the Greek Aúxvos, or perhaps the Latin luchnus (Cicero) as the German fackel comes from the Greek pakeλos (faggot), a bundle of sticks - after, a torch. But our own word torch is more evidently from the Latin tartitium, a twisted thing, now however more properly applicable to the link. Our pine torch too is obtained from the Koman tæde-slips of the tæda, or Italian pitch pine, that being the usual outdoor light of Rome; whilst Funalia, which Virgil tells us were used to light Dido's palacedependent lychni laquearibus aureis Incensi, et noctem flammis funalia vincunt.

"

is evidently from funis, a rope. Their composition was rather that of a finer kind of link, flambeaux, consisting of a centre of oakum, which was surrounded by alternate layers of rosin and crude beeswax, outside of all being a bleached coating of the latter. They were more costly than other kinds of torch, and giving a less smoky light were more generally employed for the illumination of halls, staircases, &c.

are

At what date this torch fell into disuse is a question which cannot be definitely answered, as in old times words applied to various illuminating agents, which have a very fixed and definite meaning in our day, were then interchangeable. In our translation of the Scriptures "candle" and "candlestick used indiscriminately with lamp, and, did we not know that candles proper and candlesticks were unknown at this period, we might infer that they were both in use. An explanation of this use of the words "candle" and "candlestick," however, is found in the fact that the Latin candelabrum and the Greek Avxvía, I atin luchnuchus (Cicero), meant "lampstand."

Again, in Matt. xxv. 1-5, where we find the parable of the Virgins, the word Avxvòs is rendered lamp. But a study of the

etymology of the words shows that they are derived from roots signifying to shine or burn-as candela, kavdhλa, akin to candeo, to shine (Persian, kandeel; Sans., kan)-λúxvos, lucerna, from lux, light (Sans. lok), λáuras, lampas, probably connected with lame, and the Hebrew lapad, to shine.

But although it is doubtful at what date the torch fell into disuse, it may be concluded that it was succeeded by the lamp. We find evidence of this in studying mythology. Thus Ceres, according to the old legend, sought her daughter in hell with a torch; Apuleius make Psyche drop hot oil on Cupid from a lamp. Whether candles proper, i.e. wicks surrounded with wax, were known before or after lamps had come in'o use is doubtful. Martial (first century A.D.) speaks thus co cerning the candle :— "Nomina candela nobis antiqua dederunt

Non norat parcos uncta lucerna patres."-(Ep. xiv. 43) Here, however, torch, i.e. funalia-which the old Romans in reference to its shining qualities would rather call candela than funalia-may be alluded to. In the Greek the word kavdýλa is a derivation from the Latin, not being met with until it is found in the writings of Athenæus. This author lived in the second century A.C., and in his "Deipnosophistæ" he says:

· ἐμοὶ δέ παῖ δωροίδειπνε ἀσσαρίου κανδήλας πρίω.” By that time, however, the rushlight had come into pretty general use, and no doubt it is to this that reference is here made.

But it is from a passage in Apuleius's Metam. iv. that we get the most valuable and conclusive information on this point. A noise being heard in the middle of the night, we are told that ceteris," that is with torches of pine, lamps, tallow candles, and wax the household come in with "tædis, lucerna, sebaceis, cereis, et iapers, which therefore clearly proves that candles both of wax and tallow were in use at this date. It seems, however, that the candle was probably used by the poorer people. At all events the lamp was a mark of respectability, as in another verse of Martial (Apoph. 42) we find that an apology is made for the use of a wax light instead of a lamp :

Hic tibi nocturnos præstabit cereus ignis Subducta est puero namque lucerna tuo." Juvenal (iii. 287) also speaks of the "breve lumen candela." In the British Museum, too, there is a fragment of a large candle found in Vaison, near Orange, and said to belong to the first century A.C. Such candles were probably provided with wicks consisting of the pith of rushes rudely covered with crude wax or tallow. Candlesticks for these existed, and later on they had a spike to penetrate the butt of the candle. However, the name candelabrum was more generally applied to the pillar on which the oil lamp stood or from which it was suspended. Since no attempt was made to provide for the current of air so necessary for proper combustion, these old lamps smoked exceedingly, so much indeed that it was the duty of one of the slaves of the household to go round each morning and wipe the soot from the pictures and statues. In one case, however, at the Erectheum of the Athens Acropolis, the lamp, which was of pure gold, was provided with a flue. This was a very large lamp, requiring to be filled but once in a year. Callimachus designed it for the new temple about 400 B.C., but the smoke was found to be so great an evil in anything designed for such a purpose, that the lamp was provided with a chimney in the shape of a bronze palm-tree inverted. But however magnificent and elaborate the design, it is certain that the economy of the lamp remained stationary.

It was generally filled with olive oil and provided with a wick either of oakum, or of the dearer Carpasian flax (cotton?). Occasionally, Pliny informs us, bitumen was used to fill the lamp; Italy, in some parts, being rich in springs of that mineral and petroleum. Further east, and especially among the tribes dwelling on the shores of the Dead Sea, bitumen and naphtha were much used as illuminating agents, and for other purposes. It may be suggested that the sacred pit-fire Nepti was of this nature. The well-known Egyptologist, Mr. Basil Cooper, has suggested the following as the origin of the word na htha, viz. NA, water, of Phtha, the Hephaestos, or Vulcan of Egypt's deities, the god of fire. This idea receives some support from the fact that the Indians who sold the first petroleum as Seneca oil, and used it largely in their rites of worship, termed it firewater, which name is now applied to alcohol.

Herodotus (ii. 62), writing of the Lychnokaie (feast of lamps) at Sais, in Egypt, in 450 B.C., only expresses surprise at the number of the lamps, and not at the lamps themselves, so that by this time they were getting into general use. Although their