plunger. 



34, METHOD OF ESTIMATING CHANGES IN GASES. 



confined In a 1° forming the manometer for the purpofe of comparifon, 



recurved tube by a gj a f s tube may be ufed about fixteen inches long, and one 

 b en( j. third of an inch in diameter, clofed at one end, and curved 



in fuch a manner that its open leg is parallel to its clofed end, 

 and nearly three inches long. Its capacity is determined, 

 graduated and its clofed leg is graduated fo as to form a fcale of 200 



parts. The ftandard volume of air is confined in it by a co- 

 the water kept lumn of water, four inches long ; and the height of this water 

 level, by a [ s k e pt equal in both legs at the different times of obfervation, 

 by means of a glafs tube, moveable in a perforated cork in- 

 ferted in the open end, and capable of elevating the column 

 of water in it at leaft an inch and a half. 

 Ufe of the In employing the ftandard of comparifon, for correcting the 



ftandard of remits of operations in which portions of elaftic fluids are 

 either abforbed or generated, it is only neceffary to recur to 

 the ftate of it at the beginning and end of the experiment. 

 Inftance* Thus, let n equal the quantity of elaftic fluid exiftin* after the 



experiment ; m the volume of the ftandard air before the ex- 

 periment ; and v the volume after, as exprefled in the fcale of 

 200 parts. 

 nm 

 Then — =x, which is the volume the refidual gas ex- 

 amined would occupy at a temperature and preflfure fuch as 

 exifted at the commencement of the experiment. 



By the fame method may be eftimated the volume a quan- 

 tity would occupy at fuch temperatures and preffures, as had 

 been at any time denoted upon the fcale. 

 Itlsmoftpro- From the lateft experiments that have been made *, it is 

 bable that the probable that at the fame temperatures, and under the fame 

 difturbedby die P reu *ures, equal volumes of the different elaftic fluids, in con- 

 aqueous vapour, tact with water, contain the fame quantity of aqueous va- 

 pour ; fo that in cafes when the gafes examined in the compa- 

 rative obfervations are equally faturated with water, the re- 

 fults mufl be perfectly accurate as to the relation of volume to 

 the ftate of moifture ; and, even fuppofing a difference in the 

 degree of faturation, the error arifing from this circumftance, 

 at common temperatures, would be fo fmall as to be inappre- 

 ciable. 



• Thofe of SaufTure and De Luc, and MM. Deformes and Cle- 

 ment. 



VI. Obfervations 



