published, though unaccompanied with any explanation or proof, and as the work has now arrived at its second edition, it becomes my duty to absolve its author from all responsibility; and, rather than any blame should attach to him, avow myself as the only person, who is accountable for promulgating tenets, which to many philosophers must have appeared to be visionary. It is scarcely necessary to explain what is here meant by the word silex. But, that I may be clearly understood, I shall define it to be, the very pure part of rock-crystal, and that which constitutes by far the greatest portion of all sand, flint, gravel, and other well described rocks, stones, and minerals : a substance common in every spot of the globe, in every zone, and in every climate; and an article so obvious and familiar to the meanest capacity, that any further description would be superfluous. I shall just observe, that in rock-crystal, in quartz, and in hot-springs, silex is nearly in its pure and primitive state of perfection. There is no subject, in which analogical reasoning is more admissible or more conducive to arrive at the truth, than the one before us and indeed, whenever the discussion has for its object the works of nature, as in chemistry and its sisterscience, geology, I do not see it possible how this mode of argument can be well avoided. It was analogy that led the penetrating mind of a Newton to some of the most brilliant of his discoveries; and it was the same faithful guide that conducted this immortal philosopher to predict some of the most important truths, which have since been so completely established by the experiments of his successors. The combustible nature of the diamond, and likewise that of water, are among these examples: they are facts that will for ever bear testimony to the great advantages that may be derived from this method of searching into the secrets of Nature's unerring works, and the laws which these obey. Now, to apply this mode of reasoning to the present object of research, let us consider this our sublunary world under its three grand divisions. The first, is the atmosphere, which surrounds and compresses the whole of the others; and this may be called the aëriform division of *« Chemical Catechism." nature nature. Here, it is allowed, the principal element is oxygen; but it is now in the gaseous state, that is, it is saturated with caloric. I have said, the principal element, because it is the most important of all others :-it is the matrix of fire, it is the pabulum of life; in short, such is its consequence and value to the very being of all organized matters, whether in the animal, vegetable, or mineral kingdom, that surely some more appropriate name might have been devised, than what it now bears. Though it is a digression, and remote from my plan, I shall take the liberty to hint, that merely by modifying, that is in some measure reversing, the theory which first employed the word phlogiston, both this word and the theory itself might with the greatest propriety be revived: and the word phlogiston, even in the theory of the present day, would more aptly suit our comprehension of all the properties of pure air, than that of oxygen, which implies merely the generator of vinegar or sourness, a derivation of all others the most puny and incomplete. The second grand division, is the ocean, sea, or water, which we may name the aqueous portion of the whole. Here we again recognise our oxygen, not only as the principal ingredient in magnitude, being about four-fifths of the whole, but in all other respects claiming our first attention. In this water, the oxygen is further concentrated, having lost a part of the caloric which it possessed in the gaseous form, or in the atmospheric state; so that, in this case, we may now conceive it to be, in regard to density, midway between earth and air; and that, by an abstraction of more of its caloric, it must approach nearer to a state of solidity. If oxygen, therefore, constitutes such a prominent and striking feature in two-thirds of the works of the Author of all creation-which, in these cases, is a truth that admits of no controversy. Why, it may be aptly demanded, should it not, also, form the most conspicuous ingredient in the other third, that is, the solid or real terrestrial portion of this material world? Analogy and the general complexion of all the phænomena of nature seem to answer in the affirmative, and, I think, will afford some of the most legiti mate proofs, in confirmation of the doctrine I have as sumed, the identity of silex and oxygen. This theory seems to be supported by such a mass of evi dence, that it is difficult to say where we should begin. Geology is, however, a source so prolific, that every spot of the globe teems with examples: There is not a rock, from the most huge and congregated lumps of matter, that render the face of nature at once awful and magnificent, to the most trifling pebble; nor is there a morsel of any mineral con pound, whether it be the brilliant gem or the most unfruitful and degraded soil, where, if there be an earth, a metal, an alkali, or any other salifiable or oxidable element, the saturation is not always due either to silex alone or to sʊme acid, that is, consequently, something containing oxygen. Such seems to be their equivalence, that when silex is absent some acid must prevail; and if neither be found in the association, then the earth, metal or alkali, whether potash or soda, puts on its obvious and peculiar character, such as taste, solubility, density, and the other generic qualities proper to each species After silex, there is no substance so plentiful as lime, but this is never found pure; it is either saturated with an acid, or dwindles into a tasteless inert state of aggregation with other bodies, where it is subdued and locked up by silex; so that, there is not a vestige remaining of its primitive qualities, especially those of taste and solubility. That lime, even when pure, is a compound, there is little room to doubt; and that carbonate of lime, or chalk, is produced at the expense, and through the means, of the degra dation of silex, may probably deserve a candid and minute inquiry. [To be continued.] XXXIII On the Public Utility of Medical Institutions for the Benefit of the Diseased Poor. THE foundation and support of the many medical establishments for the benefit of the diseased poor, not only in the the metropolis but throughout the kingdom, reflects the highest honour on the national character. This has long been acknowledged; and it could not fail to be highly gratifying to the public, who contribute so largely towards their support, to have a statement published annually of the receipts and disbursements of each institution, with an account of the benefits derived from them to the diseased poor. I do not think this desirable object is sufficiently attained, by the committees of a few charities circulating a report of the finances of the institutions over which they preside, among their own members or subscribers The object in view would, I conceive, be best attained by means of some periodical work, where the reports should be recorded and referred to; by which the advantages of each charity to the diseased poor would be made evident; and a liberal public would in a few years be enabled to form a correct judginent as to what kind of charitable institutions was best entitled to their munificence. The frequent, and in some instances successful, attempts to depreciate the utility of dispensaries, have led to these remarks and when it is known that for an annual sum of 2,000l. upwards of 9,000 of the diseased poor are annually admitted and attended in three of these institutions in London, (those persons being visited at their own houses who are too ill to go to the charity,) it must be confessed that dispensaries are somewhat more than "so many HOTBEDS calculated to rear and cherish their plants* for the public service." It is not my intention at present to analyse the motives which probably gave rise to the above and many similar observations, it being sufficient to record the fact; neither do I mean to advance any thing that should militate in the least against the many truly valuable public hospitals; but only to observe, that the great BENEFIT derived by cach individual inhabitant of these asylums prevents its being extended to the numbers requiring aid, their establishment not being of sufficient magnitude to lodge and feed all the diseased poor; nor would it be sound policy to extend their * The medical officers. benefits benefits so far; it being proved by the above statement, that 9,000 patients are attended annually in three dispensaries, a sum not more than adequate to the maintenance of 470 in an hospital. Greville street, Hatton Garden, February 24, 1808. JOHN TAUNTON. XXXIV. On the constituent Principles of Potash. By IN SIR, To Mr. Tilloch. March 21. In a letter I sent you, dated September 1806*, I suggested the probability that oxygen was an ingredient in the composition of potass. This has been now confirmed by Mr. Davy and although I was not right as to the quantity, I think I may claim some little merit. The rest, I said, was lime and though here I must have been mistaken as to the quantity, it still remains to be disproved that it does not enter into the composition of potass. May not lime be an oxide of the same metal as potass; or may not that metal united with other substances form lime? I think the subject worthy of investigation and unless some one abler than myself takes it up, I shall trouble you with an account of the result of some experiments which I am about to make on it. your's, MARK TAErg. XXXV. On the best Means for preventing the fatal Consequences that so frequently occur from the Dresses of Females and Children taking fire. SIR, To Mr. Tilloch. NOTHING can be more distressing to human minds than the accounts so frequently given in our public prints, of women and children being burnt to death by the accident of *See Phil. Mag. vol. xxv. p. 358. |