of (viz. gauze wire) to prevent the combustion of the inflammable gases which abound there; why, let me ask, may it not be employed to the end proposed? It is an ascertained fact that the miasmata which stagnant waters exhale is diverted by the -intervention of a few shrubs only.* It is also well known that travellers are preserved from the suffocating heat of the sinoc of the desert by merely bringing their faces in contact with the surrounding sand, the minute particles of which, in all probability, prevent the vapour from penetrating to the respiratory organs. Thus we find that all media exhibit the same phenomena when opposed by, the same difficulties; and, as far as reasoning from analogy will admit an inference, I cannot help subscribing to the belief of the practicability of what I propose. I beg leave, however, to submit it with great deference to the readers of the Annals of Philosophy, sincerely hoping should they deem it worthy of experiment, the result will be successful, since it would tend so materially to the advancement of the happiness of mankind. I have the honour to be, Sir, that Your very obedient servant, st X. On the Lunar Atmosphere. By Mr. Emmett. T c : [Hull, Feb. 15, AŠINS On Dec. 5, 1818, about 11 o'clock, the moon eclipsed la small star in the constellation Pisces, when theydeb bil following appearances were observed. SmM tri del being the illuminated part of the moon's disc, Sa the northern cusp, S S'y the apparent path of the star; the contact took place at S', and since the moon's latitude was about 2° 41′S descending, the star was obscured for a very short space of time, the apparent path of the star cutting off a very small portion from the moon's discot the star did not disappear instantly, as is always the case when the stars' path approaches nearer the moon's centre, but conti nued in contact with the moon's limb for 25% of time; for five for six seconds it gradually lost some of its brilliancy; then the form of a regular disc then appeared like a minute ray of bluish light, slowly moving along the moon's limb, losing more of its brilliancy every moment, till at the end of about 25", it disappeared in the most gradual manner. The star appears to have been kept in singe BP from Of this the Pontine marshes near Rome afford indubitable whole families have resided near the spot for years without having the mephitie vapours which those putrid waters engender, and for which no other cause can than that as a screen o of trees separates their abodes from those pestilential w + A bare inspection of the figure is sufficient to show that the minute effect of refraction through an atmosphere of very little density, can only be observed when the versed than 30 or 40, of half the arc S' is very small; when S 4 does not amount to more star must appear upon the for a considerable time, if the moon have an atmosphere capable of refracting light. view, when really behind the moon's disc, by the refraction of her atmosphere. The emersion was not observed, the star having come into view about half a minute earlier than was expected. The observation was made with a Newtonian reflector, of six inches aperture, and a very distinct power of 100: with this power, the star, before contact, presented a minute, round, welldefined disc, whose contact with, and change of place upon, the moon's limb, were most distinctly observed. J. B. EMMETT. * The existence of a lunar atmosphere is doubtful, and has been denied altogether by some astronomers. If it does exist, its tenuity must be extreme, as the brilliancy of stars for the most part is not in the least diminished by it. See in particular Col. Beaufoy's observations on this subject, Annals of Philosophy, ii. 225, et passim. XI. Mr. Murray on Dew, and on the Temperature of the Sea. (To Dr. Thomson.) SIR, Paris, Feb. 15, 1819. I was convinced of the truth of the late Dr. Wells's theory of the formation of dew from the first perusal of his very ingenious essay. Time has confirmed, not weakened the impression. On the 5th of last month in crossing the Bochetta from Genoa to Turin, at half-past seven o'clock, a. m. with a still atmosphere and serene sky, I noted the following observation, which cannot I think be explained in any other way than upon the principles laid down by Dr. Wells. The external atmosphere was 27° Fahr.; that within the coach 54°. The windows had been shut for a considerable time. The exterior surface of the glass was dry, the inner covered with a thin crust of ice, though exposed to this medium of 54°. I lowered one of the side windows about half an inch; this had the effect of causing the ice to disappear very shortly. I explain the phenomenon in the following manner: The exterior surface of the glass radiated caloric to the heavens more promptly than it received the warm impressions from within, in consequence of which the respirable vapour condensed upon the inner surface passed into the state of ice. On admitting the external air, a current was established, and the ice dissolved, though it lowered the temperature considerably. The ball of the thermometer in contact with the ice within still supported a temperature of 54°. I should add to these that no ice formed on the surface of the front windows, and these were overshadowed by the covert of the cabriolet. Now Dr. Wells has clearly proved that a cloudy sky, or the prevalence of winds, are circumstances unfavourable to the formation of dew; and that an agitated atmosphere not only prevents the deposition of dew and the formation of hoar frost, ice, &c. but dissolves them as soon as formed. Dr. Davy's ingenious researches on the temp sea will no doubt be appreciated by the navic account we are apprized of the approximation VOL. XIII. N° V. 2 B decrement of temperature. This may be the case in the ocean, but circumstances concur, I am persuaded, to modify this law as applied to the approach to land. I kept an exact register of the temperature of the sea on my passage from the Mull of Galloway to Liverpool, and on my voyage from Leghorn to Civita Vecchia; and think I have clearly proved that there is an increase of temperature in the sea off the mouths of rivers. The mean of 14 observations made in St. George's Channel is 52-8°. On approaching N.W. buoy, the temperature was 55°, and successively rose to 60° Fahr. as we approached the river Mersey: here we were among sand-banks. Again: the temperature of the Mediterranean continued nearly uniform at 70.3° Fahr.; but off the river Ombrone, in Italy (even 10 miles at sea), the temperature rose to 71-5°. The experiments were made with care, and frequently repeated. I have the honour to be, Your very humble servant, J. MURRAY. XII. On Galvanic Shocks. By Mr. John Woolrich. SIR, (To Dr. Thomson.) Lichfield, Feb. 1819. In the last (fifth) edition of your System of Chemistry, I observe the following statement, vol. i. p. 174. Speaking of the properties of the galvanic battery, and the power of the plates in giving shocks, after remarking that the shock from several hundred pairs of plates is so violent as to be painful, you say, "Even in that case, if three or four persons take hold of each other's hands and form a chain, and if the two persons at the extremities touch each an end of the pile, they alone feel the shock, while the intermediate persons are sensible of nothing." I have frequently formed a chain of eight or ten people, all of whom have felt the shock. As I conceive this erroneous statement has crept into your work through the hurry of compilation, nothing further need be said respecting it. I would take the liberty, however, of suggesting to you the propriety of noticing the error in the errata of the unsold copies; and, perhaps, a short notice of it also in your Annals of Philosophy would be adviseable for the benefit of those who have already purchased your last edition of Chemistry. I am, Sir, with great respect, Your most obedient servant, XIII. Notices communicated by C. Johnson, Esq. SIR, (To Dr. Thomson.) Lancaster, Feb. 27, 1819. 1. Meteorological Journal of Lancaster for 1818.-I transmit you Mr. Heaton's table of the results of his meteorological jour ial for 1818. It contains no account of the quantity of rain, because one of two observers who used to furnish this informa tion has removed, and the other has had the misfortune to injure his rain guage: T yewolled od men der Tabular View of a Meteorological Journal kept at Lancaster. By Mr. Heaton. THERMOMETER. Lowest. Mean. Mean diurnal variations. Highest Lowest. 26 Mean. North-west. North.com North-east. Day. Day. 80 28.86 2 28.89 Feb... Day. Day. 13-51° 18 51 March. 29 55 2 B 2 $19 [MAY, 2. Test of Gallic Acid and Silver.-Gallic acid decomposes ammonio-nitrate of silver, or a solution of oxide, or of muriate Joors of silver in ammonia, forming a very copious dense cloud and precipitate which does not entirely subside after a long time A very minute quantity of silver, or of gallic acid, may be detected and distinguished in this way. 3. Preparation of Polychroite.-Polychroite cannot be prepared by redissolving the dry extract of saffron in alcohol of sp. gr. 800. If the extract be dried until it becomes brittle, a much weaker spirit must be used to redissolve it. When the alcohol is diluted to sp. gr. 840, the extract deliquiates, but remains undissolved at the bottom of the flask, exhibiting a very beautiful purple colour. Probably sulphuric acid only produces this colour in a solution of the extract by abstracting the water. 4. Action of Sherry Wine on Iron.-A very respectable wine merchant of this town had a cask of sherry wine returned upon his hands in consequence of a gradual deterioration in taste and colour. On emptying the cask, the iron part of a cooper's tool (called a bracebit) was found at the bottom corroded in a remarkable manner at the steel extremity or head, but hardly, if at all, acted upon at the shank, which consists of malleable iron. Mr. Phillips, at p. 113 of his valuable " Experimental Examination of the London Pharmacopoeia," has stated, that "the solubility of iron 'depends very much upon its softness." But that very accurate experimenter and reasoner seems to have overlooked some solvents of iron besides tartar existing in sherry wine. Neither tartar nor vinegar has produced any effect upon a similar bracebit at all corresponding with that which took place in the sherry. I have had no opportunity of trying the gallic or malic acid, and think it better to state this trifling and probably useless fact than to offer speculation upon it. I remain, Sir, your obedient servant, P.S. Can you favour your distant readers with a more detailed character or even title title of Dr. John's Laboratorium than is to be derived from the article "Decomposition Chemical" in Napier's Supplement to the Encyclopædia Britannica? A friend of mine who has just left Glasgow for Leipsic has promised to bring me a copy of this and several other German chemical books, which I have hitherto been unable to procure. When I receive it, I shall take an opportunity of giving an account of this work in a future number of the Annals.-T. Thomson's Chemistry, iv. 50tze princio ed most attal s em betrummeq pinata enn odw bas,ered aním to basit s of ei |