« PreviousContinue »
origin from the matter of light? This appears to be the case, when the eyes of a passionate man inflamed by anger, or by love, seem to be on fire; or when the eyes ftrine fire, in consequence of a violent blow.'- This is one of the many specia mens that occur in this treatise, of the lax mode of philosophiling adopted by the Author; and which, not long since, we took occasion to expose, when we had the work of a preceding, · otherwise respectable, theorist (M. Buffon) under confidera
tion. Were this mode univerfally adopted, the lights which we owe to the Experimentalists of this and the last age would foon be obscured, and the philosophical world would again be involved in all the wordy darkness of the Peripatetics.
Thus, among the proofs which the Author adduces, to shew the great difference, and even contrariety, between the nature of light and that of fire; he urges, that Light not only enjoys an illuminating property, without producing any change whatever in the parts of the illuminated body; but likewise, a cherishing or refreshing (refocillante effeétu) and, as it were, revivifying quality: that is, a property nearly. contrary to that of heat, and fire; by which, according to their different degrees, bodies are not only inore or less changed, but are often destroyed.'
According to the Author's system, no heat, or fire, exists in the solar rays. Some of his reasons for maintaining this propofition are because, when the Almighty faid, Let there be light, &c.” fire could not then exist: for at that time, no bodies had been created on which it could act. To render the solar rays capable of producing the same effects on bodies, as are produced by fire, it is requisite that there should be a solid infiammable matter, on which they might exert their action; for the fun's rays produce heat solely by their action upon bodies.—But pafling over the Author's mode of reasoning on this subject, we need only observe, that this proposition is equally true with respect to culinary fire, when exhibited in the form of luminous rays ; particularly when the burning and luminous body is placed, for instance, in the focus of an elliptic fpeculum,
No fire, the Author continues to say, exists in the solar rays; for Boerhaave found that, even when collected into a focus, they would not produce any detonation with nitre.
But surely the learned Author cannot be ignorant, that neither the rays of common fire, nor even an ignited body in contact with nitre, will produce any such detonation, without the presence of phlogiffon, or of an inflammable substance. If he means only to prove, that there is no phlogision in the solar rays; he is con
• See Appendix to our sit volume, pag. 519.
tending for a proposition that no one, we apprehend, will oppose : bst that this is not his intention, is pretty evident from many of his arguments; such as the diminution of the solar heat at the tops of mountains; its not bearing a constant relation to the latitudes of places, or to the greater or less obliquity of the solar rays; and other matters totally unconnected with this particular circumstance.
Some of the remaining proofs of the difference between solar and common fire are-ihat the solar rays, in themselves, are certainly of the same quality in vacuo, as in the air ; but that though, when collected into a focus, they will fire gunpowder in the air, they will only cause it to meit and fume in vacuo. They have therefore, argues the Author, no heat, but that which they acquire from the air, or from certain substances floating in it.-But is it not true likewise, that common fire applied to gunpowder, will produce the same effects, under the same circumstances ? -That the solar rays, how much soever concentrated, will not produce fire, without the accesion of a combustible matter ;- but will common fire act without such an acceßion? That the solar rays have for many ages acted, and continue to act, without any diminution, and without any pabulum, or smoke : whereas, common fire is continually on the decline, requires a renovation of the pabulum, and is attended with effluvia.- But if,' says the Author, the sun be an ignited body, who set fire to this immense mass of matter? How could the whole of it, altogether, and at once, burst into Bame ? Matters exposed to the action of common fire are only kindled succelïively. Who will dare to say, that God fit created this immense globe, and then set it on fire ; which must be the commencement of its destruction ? To fuch absurdities mult those be reduced, who consider the sun as being an ignited body.'-The absurdities, however, depend only on the manner in which the Author chuses to state the circumstances.
From the confideration of fire, the Author proceeds to that of water. Thales himself scarce ascribed greater universality to that element. He contends that, at the time of the creation, the whole of the air that surrounds this globe was produced from water ; and that earth likewise owes its origin to the trans. mutation of water into that substance. He affirms, that water, while boiling on the fire, and as long as a drop of it remains, is converted not only into a dense vapour, which returns to the state of water again, but into a still rarer vapour likewise, which is real or permanent air ; but we do not here meet with a single proof of this strange proposition.
Šrom the consideration of common air, the Author is led to treat of fixed air. He proposes the question, whether, in the processes for obtaining it, it should be confidered as eductum, vel
productum; productum; that is, whether it previously exists in the substances from which it is obtained, on the addition of acid liquors; or whether it is only an extemporaneous modification of these acids. He determines in favour of the latter opinion ; but founds his determination on such grounds, as fhew him to be very little conversant, or at least very ill informed, with respect to the present state of this particular branch of knowledge.
To go even so far back as Dr. Black's discoveries, with respect to the fixed air contained in lime-ftone ;--the Author obo ferves, that Dr. Black's hypothesis on this subject was attacked, and that of Meyer was defended, by M. Crantz : and he expresses his surprise, that none of the patrons of fixed air, have hitherto (to his knowledge) attempted to defend Dr. Black's theory, as far as they had it in their power.-Paffing over Dr. Black's powerful German second, M. Jacquin, who, in 1769, verified his experiments, and confirmed his theory by new ones ; we need only to name M. Lavoisier, who, not very Jong afterward, fully established the credit both of the experiments and she theory, with a measure and a balance in his hand. To these two philosophers alone we may safely refer the learned Author, for an answer to the various objections which he here proposes against this new theory of fixed air,'-We shall only take notice of two of them,
When artificial nitre is made, by adding spirit of nitre to a fixed alcaline falt; the fixed air supposed to refide in the latter, is said to be all expelled by the acid: but if this were really the case, how happens it, says the Author, that when the nitrous acid has been expelled from the alcali, in the subsequent defiagration of the nitre with charcoal; and fresh fpirit of nitre is then added to the alcali deserted by it; as great an effervescence, and as large a quantity of fixed air presents itself as at first? Whence does this freth ftock of fixed air proceed ?
It proceeds, we will inform the Author, from the particular inflammable substance employed to expel the nitrous acid; whose place one of its principles immediately occupies at the very inftant of the deflagration. This, however, only happens when the inflanımable matter employed in the process contains fixed air: as is the case when charcoal is used. In the defiagration, the alcali receives its fixed air, or mephitic acid from the charcoal; in the very fame manner as it receives the vitriolic acid, when fulphur is employed in the deflagration. The Author must be too good a chemift not to know, that when filings of iron, zinc, &c. which contain no fixed air, are used in this process; the alcali left after the deflagration will not exhibit any appearance of fixed air, on the addition of spirit of nitre. This matter is fully explained towards the end of Dr. Prieftley's Experiments and Objervations, &c. Vol. III. p. 386.
After denying the existence of fixed air in lime-ftone, the Author endeavours to reduce the patrons of fixed air to a dilemma, by the following reasoning. It is alleged by them, that lime owes its folubility in water, to the expulsion of its fixed air, by calcination : but magnesia, treated in the fame manner, is infoluble in water. He wilhes to be informed, how effects thus contrary to each other, can be produced by one and the same cause. — But surely the inference implied in this question is highly illogical. Can any thing be more natural, than that one and the same substance may, by its presence, or absence, produce or occafion different effects in different bodies; or even in the very fame body, when the circumitances only are different?
The Author next undertakes to prove,“ beyond any possibility of doubt,' that all the earth of the present terraqueous globe was derived from water, as well as that which constitutes the bafis of vegetables and of animal bodies; and for this end, he endeavours to ascertain not only the possible, but the actual transmutation of water into earth, in various inftances. He not only relates the many well known experiments, in which this tranímutation appears to have been actually effected; but offers likewise various other observations tending to prove the possibility of this conversion; which, however, are not of such a nature as to satisfy even the least scrupulous philosopher. It is far from our intention to treat a writer of such acknowledged merit as our Author with disrespect; but we must observe that, in numerous instances, which occur in this work, he is not very nice in his proofs; but employs any one that seems to serve the present purpose, indiscriminately ;-whether strong or weak, and whether drawn from philosophy or fcripture : for to this last the Author chuses likewise to appeal, even on philosophical questions.
According to the Author, water is converted into earth, in the various procefses of vegetation, animalisation, agitation, trituration in glass mortars *, putrefaction, coagulation, by means of the sparry acid discovered by M. Scheele, and distillation. With respect to the results attending this last process, our philosophical readers may consult the particular account we gave of M.
The Author affirms that by a long continued crituration of diftilled water, without intermission, in a glass mortar, he first prodéced veficles; that afterwards the water became less fuid, and appeared, as it were, coagulated; and that at last it was changed into a light white earth, adhering to the bottom and sides of the mortar. From only one drachm of water he declares that he obtained about one fcrupule of this vihite earth; which he afirms to have found, on examination, to be of a different nature from that which can be obtained from glass.
Lavoisier's experiments ; (See Monthly Review, vol. L. Ap. pendix, June, 1774. p. 544.) or Dr. Priestley's account of his trials made on water subjected to a very strong and long continued heat, in tubes hermetically sealed ; and which are contained in his late volume of Experiments and Observations, &c.
M. Lavoisier ascribes the earth which he procured by the diftillation, or rather cohobation, of the purest distilled water, to the abrasion of the particles of the glass vessel containing it: as he found that the pelican which he employed had loft about as much of its weight, as was equal to that of the earth procured. The Author controverts this conclufion. He first questions the accuracy of the balance employed in this experiment. He does not think that M. Lavoisier used a sufficient degree of beat: [This objection, however, does not militate against the trials made by Dr. Priestley; who is inclined to suspect that his processes were not continued a fufficient length of time) but bis principal objection to M. Lavoisier's conclusion is, that the loss of weight observed in the pelican, at the end of the experiment, might, with equal probability, be ascribed to the action of the fire on its external surface, as to that of the water on its inner surface: properly observing, however, that a chemical examination of the earth procured in the process, and a comparison of it with the subtle powder of glass, would best settle this point.
Having shewn that both air and earth owe their origin to water, he confiders all natural bodies as consisting only of three principles ;—the infiammable, the saline, and water : and then resolving the saline principle into the aqueous and the infiammable, he concludes, that the principles of all natural bodies are neither more or less than two ;-carth which is undoubtedly the principle so called by Moses,' (Gen. i. ver. 1.] and the matter of light, pure fire, celestial fire, and which is denominated cælum by Mofes.' The Author endeavours to shew, how the various bodies in nature may be formed out of these two principles, in consequence of their different modifications, or the varieties introduced by figure, greater or less coheron, &c.: but he labours ftill more strenuously to shew, that his system has the countenance of Moses, in his history of the creation; where he supposes him not to have given a partial history of the creation of this earth, but of the whole visible universe. The pious Author accordingly expresses the utmof anxiety, left his philosophical and chemical principles, or his deductions from them, should be found contrary to those of the sacred historian, and_ Maximum physicuin, Mosen;'-who, we acknowledge, was undoubtedly skilled in all the learning of the Egyptians :--but how far that learning extended, with respect to the philosophical part of the present inquiry, we can