with equisetoe-and earlier still, even the soft cellular tissues of the sea weeds have not failed to leave traces behind them.

Such evidence appears to me to warrant us in supposing that the creation of the organic covering of our globe was a work of successive epochs, each one presenting a class of vegetation as highly developed as the then peculiar climatal influence would support, and each one contributing to the formation of those conditions of soil required by the more highly organised denizens of the next succeeding epoch. Whether any of these forms were permitted to survive the fearful ordeal of geological transformation, and continued to develop themselves in those localities where the changed conditions of circumstances would permit, I am not prepared to say, though I must own I am strongly inclined to favour the supposition.

If the imperfect outline I have given of this branch of the science of botany tends to infuse into the minds of any present a spirit of inquiry, a desire to dive deeper into the secrets of nature, to penetrate further than the mere superficial beauty of her garment; to study the sublimity and harmonious working of her laws, whether displayed in the organisation of a single plant, or in the wide field which the distribution of those varied and countless forms of vegetation present; I say, if I have attained this result, I shall be more than compensated.

And need I add that, to those who enter on such an inquiry, fresh beauties will disclose themselves at every step; and that the mind, while contemplating the perfection of things created, will become gradually raised and exalted to a point from which it may attain a more perfect comprehension of the power and omnipotence of the Creator.

MODERN CHEMICAL DISCOVERIES.

BY F. CRACE CALVERT, Esq., F.C.S., M. R. A. T., Honorary Professor of Chemistry to the Royal Institution, Manchester.

[The first of a course of Lectures, delivered at the above Institution. Condensed.]

PROFESSOR CRACE CALVERT stated that it was his intention to give a yearly course of lectures on modern chemical discoveries, in order to make known the chemical researches and discoveries of the day, which followed one another so rapidly that hardly the professed chemical student could keep pace with them. Persons who wished to attend these future lectures must, in order to follow him with interest and profit, be familiar with past discoveries and those which he was about to elucidate, because there was an intimate connection between them. Progress was gradual and successive in every branch of human investigation. It was very rarely that perfectly original scientific discoveries were made; they always had some link connecting them with previous discoveries. The first matter which he should bring under their notice was ozone, which was discovered in 1840, by Schönbein, who found that the oxygen of water decomposed by electricity had a peculiar odour, as well as peculiar oxidising qualities, such as to convert silver into oxide of silver, which ordinary oxygen would not do. He also found that if he placed a piece of paper, which had been dipped in a solution of starch mixed with iodide of potassium, in ozone, the

paper gradually became blue. Mr. Schönbein stated that he had also produced ozone by chemical as well as electrical means. It was now doubted, however, if ozone could be produced by chemical action; but the production of ozone through electricity had attracted the attention of a great number of philosophers. Thus, Mr. De la Rive, of Geneva, and two French chemists Fremy and Bequerel, had published interesting experiments for producing ozone with electricity. The conclusion they came to was that the new substance was not entitled to the name of ozone, but that it was nothing but oxygen in a peculiar electrical or allatropic condition. It had been ascertained for a long period that a piece of iodised paper would not become coloured in a town, while it would in the country; the conclusion was that the air in the country contained ozone, but not the air in towns. Mr. Cloez had published some papers which throw light on this question. He (Mr. Crace Calvert), thought it doubtful if ozone existed, but it was possible that the oxygen of the air might become transformed into ozonised air by means of the electricity which everywhere pervaded creation. Professor Williamson, of University College, London, was of opinion that ozone was a highly oxygenated compound of Hydrogen. Professor Andrews had published a most interesting paper, which proved that ozone was not an oxygenated compound of hydrogen when water was decomposed through a galvanic battery. By patient experiment he arrived at a result which did him credit, namely, that in 10,000 parts of oxygen, produced under the most favourable circumstances for producing ozone, there were in 10,000 of the oxygen so liberated, only 41 parts of ozone. Mr. Crace Calvert demonstrated each subject and invention he described by interesting illustrations. Carbon had long been known to chemists under three forms, as charcoal, as a graphite, and in the beautiful crystalised and valuable form of the diamond. Mr. H. St. Clair Deville had succeeded in

obtaining carbon in all these states, even of late in the crystalised or diamond form. These crystals [specimens were handed round] were as hard as diamonds, and transparent, but they were not diamonds, because they would not refract or decompose light, therefore they had not that property which made the diamond so valuable. The next substance, silicium, had drawn great attention from the scientific world during the last two years. Mr. Wöhler, a well known German chemist of high reputation, and Mr. Deville, had found a way of producing silicium, the substance which existed in silicia and rock crystals. Mr. Deville had lately found that ten per cent of silicium with ninety per cent of copper, formed a beautiful white alloy, and that one alloy containing four per cent of silicium, had the malleability and tenacity of iron, and the fusibility of copper. So valuable were its properties that the French government had ordered some cannons to be cast with this new alloy. The expense and difficulty of casting and boring large pieces of ordnance would in all probability be avoided with this new alloy. He would now draw attention to another substance belonging to the same class—“boron-which had been produced by Mr. Deville and Mr. Wöhler. It was known to chemists that boron ought to have similar properties to silica and carbon. Sir Humphrey Davy, fifty years ago, got boron in the form of black powder; but Mr. Wöhler and Mr. Deville had published within the last few months a very interesting paper detailing how they had produced boron in crystals, having all the appearance of diamonds; which crystals refracted light like diamonds, so that they could not be distinguished from them. They had not been able to get them so transparent as diamonds, but they were nearly as hard. It perfectly scratched sapphire, and no substance known, except diamond, had that property. It was very important to the lapidary, who would be able to use it for cutting stone, at a saving of expense. None of these

substances, diamond, silicium, boron, were effected by the oxygen of the air, acids, or solution of alkalies. Boron would never have been discovered had not aluminium been first discovered.

The next substance to which he would draw attention was phosphorus, which assumed two conditions under the effect of light and heat. The importance of the discovery he was about to mention was very great. The fumes of the ordinary kind of phosphorus used in manufacture were the cause of a disease which rotted the jaw bones. The new, or red phosphorus, did not give fumes in the air, and therefore produced no danger to those who used phosphorus in making chemical matches. Yellow phosphorus was also highly combustible; red phosphorus was not poisonous; while the yellow was not. It was important to medical men to know, that this red phosphorus was not poisonous, while the yellow was highly so. It had latoly been ascertained that when prepared for any length of time it underwent chemical changes, and then it acquired poisonous properties. Medical men should know this, when applying phosphorus to medicinal purposes.

Mr.

Mr. Crace Calvert next spoke of sulphur, and the action of heat upon it. Mr. Mitcherlick discovered some years ago that the sulphur which crystalised by heat, and that which gradually deposited itself from a solution in turpentine were different in their crystalline forms, one being prismatic, the other octohedral. Rose found that by heat the octohedral crystals became opaque and split into prismatic ones. It was curious that by no geometrical problem could they solve the transforming of an oblique prism into the octohedral, therefore they were two distinct crystal forms. The action of heat upon sulphur had engaged the attention of several gentlemen within the last few years. It was known that sulphur melted at a heat of 226°, and that when heated at 450° it became brown, thick, and elastic when poured in cold water. It was also known that