washing it. The captain preferred the latter method, and firmly persevered in it. The consequences were, that the lancet was kept going by the surgeon, to retard the ravages of inflammatory disease, occasioned by continual humidity; and the water buckets were daily kept plying on the lower deck, by the captain's orders, on the alleged principle of allaying the dust and sweetening the ship.'

In the following year, the same ship was commanded by another captain, attached to the same station, and performing exactly the same kind of service. This officer happened to be one of the few who recommended keeping the lower deck perfectly dry: and such were the happy consequences of this change, that not a single case of acute disease appeared for several months, and the medium number on the sick-list did not amount to one third of that of the preceding year.

I will leave the scientific world to judge, which of the above modes ought to have been adhered to; yet, I am fully convinced, both individuals had the welfare of the ship's company equally at heart. Hence, the propriety of having certain salutary regulations made official, or so intimately blended with the service, that they cannot be deviated from. It was by having demands for vegetables and lemon-juice interwoven with forms of service, that sea-scurvy was subdued; and it is only by putting certain barriers to washing decks, &c. that the dreadful class of inflammatory diseases is now to be diminished; and it was under a hope of obtaining so desirable an object, that this Essay took its origin.

Of cleaning a Ship's Hold.

THE practice of allowing filth to accumulate in a ship's hold to a great extent before it is cleaned out, is another link in the morbid chain of humidity, by which the inmates of the lower deck are often doomed to suffer.

No rule can be laid down for cleaning a ship's hold so good, as that it must be done as often as it becomes filthy; and it follows, as a consequence, that those ships, which are most famed for having their lower decks washed, soonest acquire an accumulation of filth in their holds.

In tropical climates, we are most imperatively called on to be

After the diurnal operations of bleeding and washing were gone through, the waggish tars used to say, "Now the doctor has taken his blood and the captain given his water, they hoped the purser's steward would soon follow with their grog."

punctual in this respect, in order to prevent fever being generated by such a cause.

Again, in colder regions, such punctuality is not necessary, as cold has the power of partially arresting the process of decomposi

tion.

I am here compelled to observe, that cleaning a ship's hold is a duty that is in general carelessly performed, because it is an unpleasant part of the service, and one that leaves no external mark for approbation, like washing and scrubbing. Hence, it is usually neglected or evaded, by saying there is no necessity, until fever has commenced its ravages.

Cleaning a ship's hold, however, is genuine cleanliness, and as salutary as washing the body and putting on dry clean linen; while washing decks may be compared to shifting oneself into wet clean clothes. It will appear rather paradoxical to assert, that an extraordinary ship for washing is always a dirty one; but when we recollect the general tendency of the operation is that of washing filth from the surface of the lower deck into the holds, through the medium of the scuttle-holes, &c. the observation then becomes less objectionable.

Of Bilge Water.

WATER is never obtained quite pure from nature, for even rain water is known to contain small traces of the muriatic and nitric acids and, in watering a ship from spring water, it is always found to hold a certain quantity of earthy salts in solution.

When river or marsh water is used, it is constantly found impregnated with animal and vegetable exuviæ in a suspended state, undergoing decomposition. On going to sea, after being so watered, the heat and impure air of the holds, together with the motion of the vessel, soon produce a spontaneous change in the water in cask; and that oozing through the ship's sides, and these united agencies, give origin to that fetid smell, commonly said to arise from the "Bilge Water." This is, in fact, a mixture of impure sulphuretted and carburetted hydrogen gases, varying in strength, in proportion to the quantity of foreign matter contained in the water, newness and tightness of the ship and casks, and degree of heat and motion at the time.'

1 Carburetted and sulphuretted hydrogen gases are formed in the following way: When water is partially decomposed, either by being kept long in cask, or subjected to great heat and pressure in oozing through a ship's sides, the carbon of the wood unites with the hydrogen of the water, to form an impure carburetted hydrogen gas. During hot weather, and when there is great motion in a ship at sea, this gas may be collected in the well of a

Both these gases are highly deleterious to animal life, and, from their being of greater specific gravity than atmospheric air, they will not give up their residence in the lower department of a ship (where they were generated), unless dislodged in the way hereafter to be mentioned in the chapter on Dry Rot.

Of wet Hempen Cables.

THE common practice of coiling down wet hempen cables in the tier, immediately after they have been hove in, fully saturated with moisture, is another very injurious and unskilful custom in the royal navy. First, by conveying moisture into the tier, from which a continual evaporation is kept up; and, thus, the inmates of the lower deck are not only doomed to suffer, by internal, but from all circumambient causes. 2dly. Every one who is only acquainted with the rudiments of science, must be fully aware, how much the destruction of a cable is promoted by adding moisture to the heat of the tier (the chief agents of decomposition), on a perishable article like a hempen cable.

Farther, humidity, like caloric, has a tendency to equilibrium: hence, the hammocks, men's clothes, and every article on the lower deck, absorb moisture, until they reach an equal state in point of saturation with the mean of the surrounding objects.

Should a due regard for health not be sufficient to deter us from this unsalutary practice, surely, the great expense the country is put to on that account, and the yet more important consideration of greater personal safety, ought to induce us to abandon this

custom.

Moreover, when we consider that, in many perilous situations, a cable is the only connecting link between life and death to a ship's crew, one would not, a priori, anticipate any objections to preserving it in as perfect a state as possible. I would, therefore, recommend, that cables should uniformly be allowed to dry on the main deck (except in cases where it is necessary to have it clear for action) before being coiled down in the tier.

The iron cable, from its uniformity in point of strength, and its non-absorbing qualities, possesses advantages over the perishable hempen one, both in regard to safety and salubrity, which ought not to be forgotten in comparing them.

ship's hold, by a bottle, after the same manner that gases are collected in a pneumatic trough. Sulphuretted hydrogen gas is formed thus: during the putrefaction of the animal and vegetable matter contained in water, sulphur is evolved, in union with hydrogen, to form this fetid gas.

Of Impure Air.

The vital air

Pervades the swarming sea and heaving earths,
Where teeming Nature broods her myriad births;
Fills the fine lungs of all that breathe or bud,
Warms the new heart, and dies the gushing blood;
With life's first spark inspires the organic frame,
And, as it wastes, renews the subtile flame.

DARWIN.

THE absolute necessity of animals breathing pure air, in order to enjoy good health, has been admitted, even by those who entertain opposite opinions on almost every other subject.

Even food itself is of less importance to warm-blooded animals than pure atmospheric air. The one, we only require at stated periods, but our demand for the other is continual, during the whole of our existence.

Happily for man, he has not to depend on his own industry, nor the caprice of others, for his atmospherical supply, otherwise his preservation would have been in continual danger. But the great and bountiful Author of Nature has secured us against such a risk, by the universal diffusion of atmospheric air over all habitable space. Yet, although we are liberally supplied, so far as regards quantity, we are frequently doomed to suffer from aerial changes, and their occasional insalutary impregnations. But as atmospherical mutabilities arise from causes we are seldom able to counteract, they are only to be guarded against by suitable clothing.

I

Impurities of the air are sometimes more within our range of action, being frequently generated by known causes, as putrid marshes, filth in a ship's hold, &c. and this leads me to consider its bad effects on those exposed to its influence.

It has been calculated, that the internal surface of the lungs of a man of common size, measures upwards of 21,000 square inches. It is evident, when this extensive surface comes in contact with air, loaded with moisture or charged with pestilential gases, disease must be generated in the latter instance, and heat abstracted in the former; owing to water being a most powerful conductor of

caloric.

Besides, air, thus saturated by humidity, is incapable of giving a due degree of excitement to the circulation, consequently, digestion, and all the secretions and excretions, become impaired.

This seems to be in unison with the great divine plan; something is generally left us to perform, and it is only in making such attempts that talent is developed and discoveries made.

VOL. XXVI.

Pam.

NO. LI.

M

It is furthermore certain, that moist air is lighter, and contains less of the vital stimulus, than dry air; hence, it follows, that the heat of the body is reduced two ways; first, by moisture, and secondly, by a deficiency of oxygen in the atmosphere, the source of animal heat.

Of Wind-sails and Stoves.

THE popular system of washing the lower deck would be less lamentable, if its effects were only temporary, or if we possessed the means of counteracting its baneful influence. But hitherto we know of no remedy which has the least claim to being even generally useful, and thus a strong disposition to disease is planted, with the most limited means of removing it.

Wind-sails and stoves are the means resorted to at present, for drying and ventilating a British man-of-war; and they may very properly be nominated a remedium miserabile.

In ships where wind-sails are put down every morning, after the manner of other routine duty, and suffered to remain, though rain or strong wind should supervene, they are often productive of much harm, by being a medium for the introduction of moisture and strong wind into the lower deck.

In fact, wind-sails cannot be used at all (at least with advantage), either during the presence of strong wind, rain, or calm weather; and seldom when the ship is under way.

When air is introduced into the lower deck, through the medium of these canvas conductors, they, of necessity, end abruptly near some of the men's berths; and if the wind should happen to be at all strong at the time, the current of air will be such, as to be very hurtful to those who sit in the vicinity of their termination.

Again, during the continuation of fair weather, with gentle breezes (when they are least wanted), wind-sails will have a salutary tendency, if carefully trimmed and shifted.

But whenever the wind is strong, the termination of the windsail should be directed from the men's berths towards the ceiling of the deck, by means of an elbow, to be attached and detached at pleasure, as recommended by the Right Hon. Sir John Sinclair, Bart.'

During the period I belonged to the Royal Squadron, on His Majesty's visit to Scotland, the Right Honorable Sir John Sinclair, Bart. did ine the honor to give me a plan explanatory of his "Improved Mode of ventilating Houses," and, at the same time, suggested to me the propriety of attaching an elbow to the bottom of the windsail now in use in His Majesty's ships, in such a way, that the force of the current might be expended on the ceil