It is evident that there are only three poffible ways of explaining these facts: either the galvanic action tends in each quantity of water to take away one of its conftituent parts, leaving the ather in excefs; or it decomposes the water, and, fuffering one of the gafes to be difengaged at the end of one of the wires, conducts the other, in an invifible manner, to the extremity of the others, to fuffer it to be there difengaged; or, in the last place, the water is not decompofed, but its combination with fome principle or other, emanating from the pofitive fide of the pile, produces oxygen gas, and with that emanating from the negative fide, hydrogen. The two firft opinions have been advanced in the Class by Monge, and the other in a Memoir by Fourcroy; the third be longs to fome foreigners, and particularly Profeffor Richter, of Jena. It appears to be fo much in contradiction with the whole of the other chemical phenomena, that it would have been impoffible to admit it, even if the experiment in question could not have been fatisfactorily explained in another manner. The Memoir of Fourcroy is the refult of very numerous experiments made by Vauquelin and Thenard; and he adds to a very ingenious explanation of the principal fact, a multitude of circumstances before unknown. Thefe authors admit the exiftence of a peculiar fluid which they call the galvanic, and which circulates from the pofitive fide of the pile towards the negative. According to them, this fluid, on iffuing from the pofitive fide, decomposes the water, and fuffers the oxygen to escape in bubbles; but it combines with the hydrogen to form a liquid which traverses the water, or the fulphuric acid, or the human body, in order to reach the extremity of the negative wire, where the gal vanism abandons its hydrogen, and in its turn, fuffers it to escape in the form of gas, while it itself penetrates the wire. The following is the experiment by which the authors prove that fuch is the fecret progrefs of the phenomenon :-If well washed oxide of filver be interpofed between the two waters, the negative wire, near which the hydrogen gas ought to manifeft itself, produces no effervefcence, and the oxide is in part reduced on the pofitive fide the reafon of this, fay thefe authors, is, because the galvan ic fluid, charged with hydrogen, lofes it in traverfing the oxide, the oxygen of which takes it up in re-forming the water. : A CRUICKSHANK ON PHLOGISTON. MEMOIR, by Mr. Cruickshank, of Woolwith, is inserted in the last number of Mr. Nicholson's Journal, which for its importance, merits a particular analyfis. Dr. Priestley's experiments, in his late work on the fubject of Phlogiston, were attended with fuch unexpected refults, and apparently fo formidable to the French theory of chemistry, that the philofophers of Europe feemed, as if by common confent, to have agreed to consider them as incorrect or unanfwerable; Mr. C. however, to his own credit, and that of fcience, has repeated the most striking experiments, completely confirmed Dr. Priestley's accuracy, discoverd a new gaffeous fubftance, and has adduced fresh proofs of the truth of LAVOISIER'S fyftem. Dr. Priestley, by heating together fcales of iron (the grey oxyd) and charcoal, or the fame oxyd and carbonat of barytes, obtained, befides carbonic acid a large quantity of inflammable gas. The inferences deducible, from thefe experiments against the decompofition of water by hot iron, and in favour of the doctrine of phlogifton, are fufficiently obvious, and have occafioned confiderable embarrafment to the fupporters of the anti-phlogistic theory. Mr. Cruickshank, in confequence, inftituted a fèries of experiments, in which, by heating together perfectly dried oxyd of iron and charcoal, he obtained, befides carbonic acid, a large quantity of inflammable gas; fimilar refults were perceived, when oxyds of zinc, of copper, of lead, of manganefe, were fubftituted for the iron. Hence he concludes, that all metallic oxyds, capable of enduring a red heat, will, when heated with charcoal, yield carbonic acid, and inflammable gas that thofe oxyds, in which the affinity between their component parts is the ftrongeft, yield the greatest quantity of inflammable gas; that the carbonic acid is difengaged principally at the beginning of the process, and the inflammable gas at the latter end. From experiments with metallic oxyds and charcoal, Mr. C. proceeded to examine the other fource of the gas; here, by heating the carbonats of barytes and lime with iron, he obtained, as Dr. P. had done, carbonic acid and inflammable gas. For afcertaining whether this gas was the fame with hydrogen, or any of the known hydrocarbonats, the following proofs were made:1. The Specific gravity of the gas in queftion is, to that of atmospheric air, as 95 to 100; whereas, that of the heaviest hydro-carbonat amounts to no more than 67.-2. When mixed with common air it does not explode, but burns with a lambent blue flame.-3. The product of the combuftion is carbonic acid, without any perceptible quantity of water.-4. For the converfion of this gas into carbonic acid, only 40 per cent. of oxygen is requifite. Hence this gas is effentially different from the hydro-carbonats in the total abfence of hydrogen; it confifts of 21 oxygen, and abont 9 carbon; may be properly called the gaffeous oxyd of carbon, as is bears the fame relation to carbonic acid as the gaf feous oxyd of azot does to nitrous acid. The inferences of Dr. P. effentially depending on the fuppofed prefence of hydrogent in this gas, are of confequence unfounded. C 1 TH ON THE COMPOSITION OF EARTHS. HE poffibility of decompofing the earths and fixed alkalis has of late been particularly difcuffed, and the improvements which chemistry has gained by the zeal and genius of mod ern chemifts, feems to entitle us to hope, that the earths are likely to be foon exploded from the catalogue of fimple bodies or elements. The following facts and obfervations deferve to be at tended to:-1. The cauftic ftrontian earth, barytes, and lime, are decompofed in the ftrongeft white heat, by combining them with carbon; the first is particlarly attracted by coal, and forms azote, water, and carbonic-acid, during that procefs. The decompofi tion of those bodies alfo proceeds under the blow-pipe. 2. Earths poffefs much affinity for oxygen, which is proved by the excellent experiments of Humboldt, in decompofing the pure argilaceous earth by oxygen gas; and it appears from the following facts, how great the influence of oxygen is upon the earths. 3. The fermentatio fofilis of the porcelain earth, according to fome mineralogifts, is formed by the foffil fermentation of the fieldspar, but it continues to be in this way decompofed, when it is farther expofed to the action of the air, by which means it is also prepared for the intended ufe, lofing thus its fandy particles, and becoming foft and fit for being worked. 4. The oxydated argilaceous. earth is with more difficulty diffolved in acids, than the deoxydated. Pure argil, which he happened to keep in combination with oxygen gas and water for fix months, was not perfectly folu-> ble in fulphuric acid. The folution, however, proceeded, as foon as the earth, after being diffolved by cauftic lyre in a filver cru cible, was precipitated by acetous acid, by which it seems probable, that the cauftic fixed alkali deprives the argillaceous earth of its oxygen in the glowfire. Hence it may be explained, why the fapphire is foluble in acids, after being burnt with alkali, &c. 5. It deferves to be attended to and proved by farther experiments, what the late Mr. Girtanner has conjectured of the oxydation of earths. 6. The earths are formed in plants and animals from elements, which they receive with their nutriment, and through the mediums with which they are furrounded. The interesting experiments of the ingenious Vauquelin on the formation of the calcareous earth in hens, are known to every chemist. The earths contained in plants are the fame, even when they grow in different foils, from which, accordingly, they do not originate. 7. Earths are alfo formed in the atmosphere, which appears from the late obfervations of ftony males having fallen from the atmosphere. If we dare acknowledge the hydrogen, oxygen, and azote, as the elements of the earth, that phenomenon will be eafily explained. From these remarks we may conclude, that very little is to be de pended on the analyfes, which have hitherto been made of terreous fubftances. Profeffor LAMPADIUS is at prefent much engaged in experiments to afcertain the nature of filiceous earth, which he conceives to be nothing but argilaceous earth in the highest degree of oxydation, and which is changed into argillaceous earth by treating it with deoxydant fubftances. It feems, therefore, probable that feveral foffils, which, according to their external or cryet ogynoftic figns appear to be filiceous, are changed in the hands of chemifts into argillaceous earth! Though confcious of the boldnefs of this affertion, the Profeffor obferves, that in different analyfes of the fame fubftances he has fometimes obtained a greater, fometimes a lefs, quantity of argillaceous or of filiceous carths, which he afcribes to the above circumstance. On the whole he thinks, that earths, as well as fixed alkalis, are compofed of azote, hydrogen, and oxygen. ACCOUNT OF A SINGULAR INSTANCE OF AT-* DEAR SIR, 4 HASTINGS, AUGUST I, 1707. N Wednesday July 26, about five o'clock in the afternoon, while I was fitting in my dining-room at this place, which is fituated upon the Parade, close to the fea-fhore, nearly fronting the fouth, my attention was excited by a number of people running down to the fea-fide. Upon enquiring the reafon, I was informed that the coaft of France was plainly to be diftinguished by the naked eye. I immediately went down to the fhore, and was furprifed to find that, even without the affiftance of a telescope, I could very plainly fee the cliffs on the oppofite coaft; which, at the nearest part, are between 40 and 50 miles diftant, and are not to be difcerned, from that low fituation, by the aid of the beft glaffes. They appeared to be only a few miles off, and feemed to extend for fome leagues along the coaft. I purfued my walk along the fhore eastward, close to the water's edge, converfing with the failors and fishermen upon the fubject. They, at first, could not be perfuaded of the reality of the appearance; but they foon became fo thoroughly convinced, by the cliffs gradually appearing more elevated, and approaching nearer, as it were, that they pointed out and named to me the different places they had been accustomed to vifit; fuch as the Bay, the Old Head or Man, the Windmill, &c. at Boulogne; St. Vallery, and other places on the coaft of Picardy; which they afterwards confirmed when they viewed them through their telescopes. Their obfervations were, that the places appeared as near as if they were failing, at a fmail distance, into the harbours. Having indulged my curiofity upon the fhore for near an hour, during which the cliffs appeared to be at fome times more bright and near, at others more faint and at a greater distance, but never out of fight, I went upon the eastern cliff or hill, which is of a very confiderable height, when a most beautiful scene prefented itself to my view; for I could at once fee Dengenefs,* Dover cliffs, and the French coaft, all along from Calais, Boulogne, &c. to St. Vallery; and, as fome of the fishermen affirmed, as far to the weftward even as Dieppe. By the telescope, the French fishing-boats were plainly to be feen at anchor; and the different colours of the land upon the heights, together with the buildings, were perfectly difcernible. This curious phenominon continued in the highest fplendour till paft 8 o'clock, (although a black cloud totally obfcured the face of the fun for fome time,) when it gradually vanished. Now, Sir, as I was affured, from every inquiry I could poffi bly make, that fo remarkable an inftance of atmospherical refrac tion had never been witneffed by the oldest inhabitant of Haft. ings, nor by any of the numerous vifitors (it happened to be the day of the great annual fair, called Rockfair, which always attracts multitudes from the neighbouring places), I thought an account of it, however trifling, would be gratifying to you. The day was extremely hot (68° at 10 A. M. 76° at 5 P. M.) I had no barometer with me, but fuppofe the mercury must have been high, as that and the three preceeding days were remarka bly fine and clear. To the best of my recollection it was high water at Haftings about two o'clock P. M. Not a breath of wind was ftirring the whole of the day; but the fmall pennons at the maft-heads of the fifhing-boats in the harbour were in the morning at all points of the compafs. I was a few days afterwards at Winchelfea, and at feveral places along the coaft; where I was informed the above phenom enon had been equally visible. ILLUMINATION OF ROTTEN WOOD. HE illumination of rotten wood has been of late a fubject of inquiry and difcuffion among naturalifts. The late M. SPALLANZANI maintained that there is a perfect analogy between the illumination of rotten wood, and the artificial phofphorus ; and he imagines, that in the putrid fermentation, the hydrogen and the carbon of the wood come more easily in contact with the oxygen of the atmosphere, by which combination a flow combuft *The cape of land called Dengenefs, which extends nearly two miles into the fea, and is about fixteen miles distant from Haftings, in a right line, appeared as if quite clofe to it; as did the fishing-boats and other veffels which were failing between the two places: they were likewife magnified to a great degree. L |