cannot derive the whole, nor even the principal part, of their folid matter from the ground. They muft poffefs, therefore, a power of converting air and water into their proper fubftance. Perhaps the charcoal, which appears fo important in the vegetable economy, is chiefly feparated from the carbonic gas diffufed through the atmosphere, of which it conftitutes a hundredth part. These fecretions, however, muft coft the plants an effort, which, if auxiliary nutriment be too fcantily fupplied by the foil, will mount to such a pitch as to exhauft them and cause them to ficken and pine. We feldom confider that these organic bodies poffefs the principle of life. This is the main object to which our inquiries fhould be directed. The various manures, it is highly probable, are useful principally by acting as ftimulants, which excite the vascular fyftem in vege tables to perform vigorously its proper functions. The eminent advantages of dung itfelf in fertilizing land cannot be attributed specially to the carbone which it fupplies; for, after it is reduced by age into perfect mould, it produces very flight effects it becomes effete, a mere caput mortuum. Hence cal careous matters have a more permanent influence.

SCIENCE. Chemistry.

1. A method of preparing a fulphureous Medicinal Water. By the Rev. Edward Kenney.-It is directed to grind four drachms of the flowers of fulphur with an equal quantity of magnesia in a glass mortar, to work up the mafs gradually with water to the amount of a quart, and then to pour the liquid mixture into a clofe veffel, which may be conveniently fhaken two or three times every day for three weeks. After it has now fettled for two days, the liquor is to be decanted. The fame ingredients will impregnate a like quantity of water two or three times, to an equal degree of ftrength. One ounce of this folution, diluted with a quart of pure water, forms a medicine fit for use. It is an effectual remedy for the chronic rheumatism and for all cutaneous diforders. It also proves beneficial in cafes of fcrofula and of worms.

2. On the folution of lead by lime. By Robert Percival, M.D. M. R.1. A.-The milled lead which lined the infide of a water ciftern being much corroded, the plumber employed to repair it imputed the accident to fome mortar, which had fallen and lodged at the bottom of the ciftern. This obfervation prompted Dr. Percival to make feveral experiments, with a view of ascertaining the action of lime on lead. The refult was that lime acts imperfectly, if at all, on lead, without the affiftance of air to oxydate the metal. He therefore tried the effects produced on lead at its diferent ftages of dation.

ed twelve

Twelve ounce measures of pure lime water, kept warm in three clofe veffels for a month, were found to have diffolved each 5 grains of minium, 6 grains of litharge, and ro grains of the oxyd of lead precipitated from the nitric acid by ammoniac. It appeared that the prefence of atmospheric air was neceffary to the production of the black precipitate afforded by the folution, in contact with fulphurated hydrogenous gas. Dr. P. conjectures, with much probability, that this compound gas being decompofed by the oxygene contained in common air, its fulphur is let loofe, and combines with the lead, to form a kind of galena in the humid way.

3. Experiments on a new earth found near Strontion in Scotland. By Richard Kirwan, Efq. LL. D. &c.-The recondite diftinctions of mineral fubftances are often as important in fcientifical investigations, as those which are more obvious and apparent. The difcoveries of the difference between plumbago and molybdena, iron and manganefe, the calcareous and the barytic earths, have effentially contributed to the advancement of chemical knowlege. Repeated occurrences evince the danger of relying too confidently on pre-conceived theories. We are here made acquainted with a new earth, analogous in appearance to the calcareous and barytic, but actually different from them, and qualified to occupy an intermediate place. Dr. Kirwan received the firft notice of this fubftance, which he calls the frontionite, from the ingenious Dr. Crawford, in the year 1790. His attention was afterward attracted by an account of it which M. Sulzer inferted in the Miner's Journal for February 1791. Yet our author's experiments on the Strontion earth were not begun till October 1793. Its fpecific gravity is from 3.4 to 3.6; its colour is whitifh with a green caft: it is of a medium hardness and transparency: it prefents a ftriated fracture, and is very brittle. Expofed to a heat of 130° of Wedgwood's pyrometer, in common clay crucibles, it very readily vitrifies where it touches the fides of the crucible. Three parts of it to one of argill, urged with a heat of 150°, melted into a black compound mafs, above enamel and below porcelain. The fame experiment performed with common lime afforded only porcelain. A mixture of 67 parts of filex, 23 of argill, and 10 of ftrontionite, melted at the 114 into a greyifh white porcelain: but, when common lime was fubftituted, it required a heat of 145° to run into a femi-transparent frothy enamel. In general, the frontion. lime is more eafily fufed, and might be advantageously employed as a flux in certain refractory ores. It has a ftronger taffe than common lime, and is a much better teft of the prefence of carbonic acid gas. The Strontion lime heats more

violently

violently when wetted, and diffolves more copiously in water: but the most remarkable circumftance is that a faturate folution of this new lime, fet in a cool place, will fhoot into tranfparent rhomboidal cryftals. The ftrontionite diffolves very readily and with confiderable effervefcence in the marine acid. The addition of the fulphuric, tartaric, and faccharine acids produces copious and almoft infoluble precipitates. Carbonated alkalis and lime, but not carbonated barytes, likewise occafion precipitates. Strontionite will hardly diffolve in the nitric acid, unless this be confiderably diluted. The folution will not, like that of barytes, difcolour litmus. By flow evaporation, it yields crystals, which decrepitate and fufe in the fire. The fulphuric acid has fcarcely any action on this stone, if not much diluted. The acetous acid diffolves it feebly, and affords ftelliform efflorefcent cryftals.-The affinities of the Strontion earth feem moft to approach thofe of the barytic, but they are inferior in degree. We understand that Mr. Hope, profellor of chemistry at Glafgow, has gone over the fame ground, in a paper lately read before the Royal Society of Edinburgh.

4. On the power of fixed cauftic alkaline falts to preferve the flesh of animals from putrefaction. in a letter to the Rev. George Graydon, from the Rev. Hugh Hamilton, D. D. &c.This article was occafioned by the ingenious theory of Mr. Graydon already confidered, to which it is intended as a fupplement. Yet it has no immediate reference to the fubject in queftion; for the property of cauftic alkali to refist putrefaction cannot be legitimately extended to quicklime, though both thefe fubftances have been comprehended under the loofe denomination of alkaline faits, The Dean argues, indeed, rather whimfically, but the hiftory which he gives of his progreffive conjectures is curious and amufing. Nor is the antifeptic quality of potafh to be reckoned a novelty. During the hardfhips of their memorable ftruggle for emancipation, the Americans were often obliged, by the want of regular fupplies, to ufe fresh wood-afhes inftead of common falt in curing their provifions.

SCIENCE. Aitiology.

On the nature and limits of Certainty and Probability. By the Rev. George Miller, r.T. C. D. & M. R. I. A.-This dif courfe does not claim the merit of much novelty or depth of penetration, but it is fenfible, perfpicuous, and orthodox. The author endeavours to fhew that the abftrufe queftions of cause and effect, of liberty and neceffity, are placed beyond the reach of the human faculties. To fupport this mortifying pofition,

he

he leads forth in hoftile array the redoubted champions of metaphyfics. Where the conteft remains undetermined, he infers that it cannot be decided in the prefent condition of man. The arguments employed by Berkley, Hume, Priestley, and Gregory, pafs under fuccinct review. That the Neceffarians have been guilty of fallacious reafoning feems not fully eftablifhed but their late antagonist is plainly convicted of miftaking the nature and extent of the fubject in debate. To use Mr. Miller's own words- The attempts made by Dr. Prieftley and Mr. Hume to establish the doctrine of Neceffity, have, I imagine, been fhewn to belong to that clafs of inconclusive reafoning which logicians denominate Petitio Principii, and Dr. Gregory's attempt to overthrow it to belong to the clafs called Ignoratio Elenchi; whilft on the question of Materialism Doctor Priestley and Bishop Berkley refute each other by contradictory arguments.'

To follow the author's train of argumentation would draw us into a maze of unprofitable fpeculations. We will only observe that he fhews a difpofition to adopt certain metaphyfical axioms, which he deems to be felf-evident, but which are really the affumptions of vulgar experience, and conftitute the great fource of error and perplexity in fpeculative philofophy.

SCIENCE. Mifcellaneous.

1. On a new kind of portable Barometer for measuring heights. By the Rev. James Archibald Hamilton, D. D. M. R. I. A.Those who are acquainted with the exquifite mechanism of the famous Ramfden will hardly be inclined to admire the improvement here propofed. Inftead of the leathern bag which confines the mercury in the common portable barometer, Dr. Hamilton fubftitutes a cylindrical ciftern of ivory with a screwed bottom and an open top, fomewhat contracted into a fhoulder that receives internally a found, clean, and porous cork, through which the glafs tube is nicely inferted and pushed down midway. The conftruction depends on this principle, that fpungy cork affords a ready paffage through its pores to the particles of air, but prevents the efcape of quick filver, unlefs a very powerful preflure be applied. The fact, however, is not precifely ftated. It is not through the pores of that fubftance, but through the minute interftices between the cork and the infide of the ivory cylinder, that the air infinuates itself. Accordingly, fome caution and experience are requifite to prevent the stopper from being fitted too tight. Nor can the obferver be always affured that the confinement of the cork will occafion no inaccuracy in the refults; for it will evidently require a confiderable time, through the extremely flender communications,

munications, to restore the balance between the external and internal air, if ever that balance can rigorously obtain. Dr. H. gives very copious and circumftantial directions for the conftruction, adjustment, and application of this inftrument. He remarks that mercury is beft cleaned by fhaking it repeatedly in a phial with fresh portions of water; a procefs of which we have often experienced the benefit. To correct the errors of altitude caufed by the fluctuation of the furface of mercury in the bafon, he advifes us to compute tables from the proportion which the aperture of the tube bears to that of the cylinder. The precepts for calculating heights from obfervations of the barometer are prefented by him fomewhat fimplified, and in a practical form. He propofes to delineate vertical fections of a country, by means of a series of fuch obfervations taken during fettled weather.-An engraving is added.

2. A letter to the author of the preceding paper, with remarks and hints for the further improvement of barometers. By H. Hamilton, D. D. Dean of Armagh, F. R. S. & M. R. I. A.As the pores of cork may in time become choaked with duft or humidity, the Dean propofes that the box fhould have a top of ivory with a hole to drop in a floating gage, and which might be occafionally ftopped with a peg or fcrew, to render the inftrument fafely portable. Inftead of making tables for correcting the error occafioned by the variation of the level of the mercury in the bafon, he thinks it would be more convenient to contract proportionally the divifions of the scale. This obvious plan is illuftrated at great length. It is fuggefted that thefe close barometers would anfwer equally at fea. The hint deferves attention. In reality, the very defects of the conftruction of fuch inftruments prove advantageous on fhipboard; fince, being very gradually affected by any change, they are lefs apt to be difturbed by the working of the veffel. The profecution of this idea may lead to the invention of that great defideratum, the marine barometer.

3. Extract from a paper on furveying. By Thomas Meagher, near Palace Grene, in the county of Limerick.-The purport of this extract is to recommend, for the convenience of the land furveyor, instead of the uniform partition of the compafs into degrees, an unequal divifion which fhall exhibit, on infpection, with fufficient precifion, the fine and cofine of the angle measured, and thus fupercede the neceffity of having recourse to trigonometrical tables.-A drawing is annexed.

REV. OCT. 1795

[To be continued.]

Q

ART.