before. He relates the various improvements made in these machines in France and Italy, and particularly by Mr. Cuthbertson at Amsterdam, who brought that kind of machine to perfection, and still continues to make them in Poland-street, London. 8. On the Degree of Salubrity of Common Air at Sea, compared with that of the Sea Shore, and that of Places far removed from the Sea. Phil. Trans. 1780, p. 354.-He tried air by "Fontana's method at the mouth of the Thames, and afterwards at Ostend, and in various parts of the Netherlands, France, and Germany. He, concluded from his observation, that the air is purer at sea than over land, and purer on the sea shore than at a distance from the ocean. But these inferences were made from too limited a number of experiments. Indeed only one, or at most two experiments were made at sea. It is now perfectly established that there is no difference whatever between air at sea and air at land. The supposed differences originated entirely from inaccuracies in the mode of making the experiments, and disappeared as soon as chemists fell upon accurate methods of analyzing common air. 9. Experiments upon Vegetables, discovering their great Power of purifying the Common Air in the Sunshine, and of injuring it in the Shade and at Night. To which is joined a new Method of examining the accurate Degree of Salubrity of the Atmosphere. London, 1779.-This is an octavo volume of 302 pages, which Dr. Ingenhousz published in 1779, just before setting out for the continent. He gives an account in it of a set of experiments which had occupied him incessantly for about three months during the preceding summer. Only two points are established in this book. 1. That the leaves of plants give out oxygen gas when exposed to the sun under pump water. 2. That the proportion of oxygen in the air immediately in contact with plants is diminished during the night. But whether this is owing to the absorption of oxygen, the emission of carbonic acid, or the conversion of the oxygen into carbonic acid, is not ascertained. Dr. Ingenhousz, at the time he made his experiments, had no accurate ideas respecting the composition of air, nor respecting the action of nitrous gas on air. He was not aware of the different nature of hydrogen and carburetted hydrogen gas, and perpetually confounds them together. M. Theodore de Saus, sure's experiments on this subject are much more precise; though even he has not thrown so much light upon it as is to be wished. Dr. Ingenhousz in this case, as in his explosions with common air and ether, had the merit of commencing the investigation; but his progress in it was very small. The method of determining the goodness of air, described in this book of Dr. Ingenhousz, is merely the Abbe Fontana's, a little abridged, and throws no additional light upon the constitution of air. - 10. Some further Considerations on the Influence of the Vegetable Kingdom on the Animal Creation, Phil. Trans. 1782, p. 426. Our author's opinion that vegetables emit oxygen gas when growing in the sun, and that the injury done to the air by the breathing of animals and by combustion is in this way repaired, having been called in question by some persons, and it having been alleged that it was altogether refuted in Dr. Priestley's fifth volume of experiments on air, Dr. Ingenhousz made a public exhibition of the most decisive of his former experiments to a number of his scientific friends. He boiled pump water for two hours to deprive it of its air. It was then put into glass vessels placed inverted over mercury, to shut out the communication with the atmosphere. Some conferva rivularis was put into two of these glasses, some pieces of cloth into other two, and nothing in other two. The first two glasses began in three days to yield oxygen gas, which on examination proved very pure, and the conferva, gave out altogether about eight times its bulk of this gas. In 10 days, it ceased to vegetate, and began to decay. The cloth gave out no air whatever; neither was any air collected in the jars into which nothing had been put even at the end of some months. A glass containing pump water unboiled began to yield air much sooner, and it yielded a greater quantity; but it was not so pure. 11. Nouvelles Experiences et Observations sur divers Objets de Physique. A Paris, 1785.-This is chiefly a French translation of the papers of Dr. Ingenhousz, already printed in the Phil. Trans. He was induced, he tells us in the preface, to translate them himself, because all the translations which he had seen contained mistakes which materially altered his meaning. In his own translation, he was enabled to rectify these mistakes; and he likewise added some additional illustrations, which he thought likely still further to elucidate the subject. It will only be necessary, therefore, to notice the papers which made their first appearance in this octavo volume of 498 pages. The first paper is an outline of the Franklinian theory of electricity; very short; but clear and precise; and exhibited without any mathematical phraseology. In this respect, he followed the example of Dr. Franklin himself. The second paper is a theory of the electrophorus, more detailed than the paper on the same subject in the Transactions, but quite the same in point of theory. The third paper is of some length, and consists of a set of observations on a question at that time agitated with great keenness in England; whether thunder rods ought to terminate in points, or round knobs. The question had originated in the gunpowder magazine at Purfleet having been struck with lightning. A committee of the Royal Society had been appointed to investigate the subject. From the report of this committee, Mr. Wilson dissented. He affirmed that the extre mity of thunder rods should be blunt. He exhibited a set of experiments in support of his opinion in the Pantheon, at which his present Majesty attended. The King adopted the opinion of Mr. Wilson, and altered in conformity with it the thunder rods attached to St. James's Palace. But Mr. Wilson made no other convert the dispute continued for a considerable time; but seems to have terminated in favour of pointed thunder rods. Dr. Ingenhousz in this paper gives his reasons for considering pointed rods as the most proper in conformity with the original proposal of Dr. Franklin; and his reasons appear perfectly satisfactory. It seems unnecessary to state them here, as I am not aware that any person at present supports the doctrine of Mr. Wilson. The fourth paper is a description of an electrical machine used by our author for various purposes. It consisted of a piece of strong silk suspended against the wall of a room, to which was attached a rubber of hare skin, or cat skin. He used it for charging small Leyden jars of a peculiar construction, which he describes. In the fifth paper he describes a small pocket electrical machine, intended for producing a spark sufficient for firing an inflammable air pistol. In the sixth, he gives a description of the mode of burning camphor and phosphorus in oxygen gas, and describes the bril liancy of these experiments with rapture. In the seventh, we have a contrivance for producing a vacuum by the property which charcoal has of absorbing air. It is needless to observe that there seems little probability of any such substitute for an air pump being of much utility. In the eighth paper, we have a description of a method of lighting a candle by means of an electrophorus and an inflammable air lamp. The invention belongs to Strasburg. At present we are in possession of better methods of accomplishing this object than those described in this paper. In the ninth paper, he describes his inflammable air pistol. This contrivance is too well known to require any details here. The tenth paper is a description of the mode which he employs to collect carburetted hydrogen gas from the bottom of stagnant water. The eleventh and twelfth papers are translations from the Transactions. The thirteenth paper is on oxygen gas. He procured it from saltpetre, and he conceives that it would be a medicine of very great efficacy if it were given to patients ill of certain diseases, to be respired instead of common air. This opinion has not been verified by subsequent trials. The fourteenth paper is on the salubrity of the air above the sea compared with the air at dry land. It is a translation from the Transactions. In the fifteenth paper he gives us an account of some attempts to make artificial magnets after the manner of Dr. Gowan Knight; but these attempts were not very successful. In the sixteenth paper, he gives his theory of gunpowder. He expatiates at greater length; but the theory is precisely the same as that which he had already given in the Transactions. The seventeenth paper is an application of the same theory to fulminating powder. The eighteenth paper is one of the most valuable in this volume. It consists in a set of experiments made to determine which of the seven metals, gold, silver, copper, tin, steel, iron, and lead, conducted heat best. The mode of making the experiment was contrived by Dr. Franklin, who likewise supplied the materials. Wires of each of these metals of the same length and thickness were coated with wax, and their ends dipped into boiling water. The wire on which the wax was melted and highest up was reckoned the best conductor. Silver was found the best conductor, and lead the worst in all the experiments. Copper was the next best conductor, gold the next best, tin, steel, and iron, next best. In the last paper contained in this volume, Dr. Ingenhousz describes his mode of burning iron wire in oxygen gas, and his attempts to burn the other metals in the same gas. These last attempts, except with platinum wire, had not been successful. These are the only writings of Dr. Ingenhousz which I have had the opportunity of perusing. They contain, I believe, all the additions of any importance which he made to chemistry or electricity. His turn of mind did not lead him so much to the investigation of the properties of bodies as to the discovery of what he considered to be striking or brilliant; and having got something of this kind, he seems often to have remained satisfied without any attempt to investigate what actually happened during the experiment. Thus the analysis of the combustion of iron wire in oxygen, and of the vapour of ether in oxygen, he left to Lavoisier and Cruikshanks, who, by investigating them with care, established important theoretical points in the science of chemistry, and thus contributed materially to improve it. ARTICLE II. Contributions towards the History of Anthrazothionic Acid, discovered by Porrett, and called by him Sulphuretted Chyazic Acid. By Theodor von Grotthuss. (Concluded from p. 50.) Sect. 17.-By this stochiometrical analysis, we find the proportion of water in the copper anthrazothionhydrate determined in sect. 14 by an empirical way very completely confirmed; for the eighth part of a hundred is 12-5; and our number comes out 12:63, which is so near a coincidence that we may consider the experimental and the calculated numbers to coincide. It appears also, that the view of the subject stated in a former section as probable, corresponds correctly with matter of fact; for the hydrogen of the acid added to ths of the oxygen of the oxide gives a quantity of water amounting exactly to 4th of the whole weight of the anthrazothionhydrate. We shall see likewise below how exactly the hydrogen of the anthrazothionic acid, derived from the same view (namely, 0.067 hydrogen in 1-510 acid), corresponds with the same constituent obtained in quite another way. Every hypothesis ceases to be a mere hypothesis when the phenomena connected with it, being subjected to mathematical calculation, correspond exactly, not only with each other, but with the hypothesis itself. It may then be considered as nothing else but a bare statement of a set of facts, and is raised to the rank of that highly scientific term-a theory. Sect. 18. Experiments to determine the Constituents of Anthrazothionic Acid.--I got blown in a glass-house a number of small retorts, of the shape d, terminated by a long bent tube, and having a mouth, a. These retorts I find very convenient for small chemical experiments. Through the mouth, a, of one of these retorts, I introduced a portion of anthrazothionate of potash in a crystallized state, and poured over it a concentrated solution of chlorine. Immediately the mouth, a, was shut, and the extremity of the bent tube introduced into the vessel, b, containing lime water. Chemical action immediately began, and it was accelerated by applying heat below the retort, d. The pheno سع mena which took place were effervescence, a considerable precipitation of sulphur in the retort, d, and the evolution of bubbles of gas which rendered the lime water in the vessel b milky.* After the solution had been made boiling hot, and the chemical action appeared over, I collected the whole of the precipitated sulphur upon a filter, the weight of which had been previously determined. It was washed carefully clean by repeated affusions of water, exposed for some days to the summer temperature of the air, and finally dried upon a warm plate. In this state I found that the filter had increased in weight 2 gr. This increase was wholly owing to the presence of pure sulphur, easily recognisable by its properties. The filtered liquid contained a portion of sulphuric acid formed dur The vessel b must be rather long, and it must be filled with lime water; and the bent glass tube which terminates the retort ought to terminate in a very narrow mouth, that the lime water may come in contact as much as possible with every part of the evolved gas. |