1824.] Scientific Intelligence. 393 



In another set of experiments with the same chronometer, Mr. H. 

 placed it in a condenser, under an atmospheric pressure of 45 inches, 

 when its rate changed to — 4"4 ; ani on increasing the density of the 

 air to a quantity denoted by 60 inches of mercury, the daily variation 

 farther declined to — 8" # 2. 



In another remarkable experiment, Mr. Harvey found, that when the 

 rate of a chronometer was + 23""5, under a receiver having its air 

 exhausted to a quantity denoted by half an inch of mercury, the rate 

 was altered to — 17"'2, when the air was increased to a density cor- 

 responding to 75 inches of quicksilver ; the rate of the time-keeper, 

 under the ordinary circumstances of atmospheric pressure, being 

 + **7. 



Mr. H. has, we understand, drawn from it several important conclu- 

 sions. For example, that a chronometer constructed in London, 

 nearly on the level of the sea, would undergo an alteration of rate, 

 from difference of atmosphere alone, if transported to Geneva, to 

 Madrid, to Mexico, or any other place, situated much above the level 

 of the place where it was constructed. 



III. Cheltenham Water. 



Mr. Faraday has examined the water from the Orchard well at the 

 above place. A pint of this water yielded : 



Carbonate of lime ; 1 "6 



Sulphate of lime 145 



magnesia 124 



soda 3*7 



Muriate of soda 97-0 



129-2 

 Besides which the water contained a portion of carbonic acid ; and 

 a small quantity of peroxide of iron had settled at the bottom of the 

 bottle. By using two tests suggested by Dr. Wollaston, this water 

 was also found to contain small portions of nitric acid and potash. 



On adding sulphuric acid to a portion of this water, in quantity 

 abundantly sufficient to decompose all the salts subject to its action, 

 and boiling the acidulated water in a flask with a leaf of gold for an 

 hour, the gold either in part or entirely disappeared, and a solution 

 was obtained which, when tested by protomuriate of tin, gave a deep 

 purple tint. Hence the presence of nitric acid, originally in the water, 

 was inferred, and that no mistake might occur, a solution made in 

 pure water of all the salts, except the nitrate found in the water, 

 was boiled with some of the same sulphuric acid, and tested by the 

 same muriate of tin ; but in this case no colour was afforded, nor any 

 gold dissolved. 



The potash was ascertained to be present by evaporating a quantity 

 of the water until reduced to a small portion, filtering it, and then add- 

 ing muriate of platina in solution. Three pints of the water, evapo- 

 rated until about an ounce of fluid remained, gave an abundant pre- 

 cipitate of triple salts of potash and platina. In cases where small 

 quantities of the waters were tried, it was necessary to let the liquid 

 •fand an hour or two after applying the muriate of platina, but the 

 triple salt always ultimately appeared. — (Royal Institution Journal, 

 vol. xvii. p. 179.) 



