370 AFFINITIES OF COMPRESSED CASES. 



to effect their efcape. But not to trouble you any further 

 with the obftacles that occurred, and which are mentioned 

 only to prevent unneceflary expence to others, I have at laft, 

 by Mr. Cuthbertfon's afliftance, procured a conne&ing-tube, 

 to which a fpring-valve is adapted that has hitherto anfwered 

 every purpofe. See Plate XIV. Fig. 2, 3, 4, 5, 6. 

 Inftruments The instruments which I now ufe, are, lft. An exhaufling 



auL U r? d bythe ty rm g e ; 2d - A condenfing-pump, with two lateral fprings for 

 Pump. different gafes ; 3d. The connecting fpring-valve ; and laftly, 



glafs receivers, which (hould have been of various fizes, but 

 the one mentioned above having burft, that which I have 

 Glafs receiver, principally ufed in the following experiments, is of about five 

 cubic inches and a quarter in capacity, and made of glafs well 

 annealed and a quarter of an inch in thicknefs. Befides thefe 

 infrruments, I have occafionally applied Mr. Cuthbertfon's 

 Syphon gage, double fyphon-gage (See Fig. 6), by which the number of 

 atmofpheres condenfed in the receiver, or rather the elaftic 

 power of the gafes, may be meafured ; but this is rendered 

 of lefs fervice, becaufe a flop-cock muft then be placed be- 

 tween the receiver and fpring-valve, which frequently impairs 

 the whole experiment; and alio becaufe, after a certain de- 

 gree of condenfation, and more particularly upon the admix- 

 ture of the gafes, new affinities ufualfy take place, which tend 

 Eighteen at- to diminish the elaflicity : the greateft number of atmofpheres 

 mofpheres rov g a g e j^g ^ et me afured, is eighteen. Thefe, Sir, with 



fome bladders and flop-cocks, various iron fcrew-keys, and a 

 wooden' guard for the legs in cafe of burfling, conftitute the 

 principal part of the reqaifite apparatus. 



I now proceed to the experiments, premifing that the firft 

 four were made with the imperfect apparatus, when the gas 

 was continually making its efcape through the flop-cock. 



Experiment I. 



Erp. i. Hldro- Into the glafs receiver, of three cubic inches and a half 

 gen, oxigen, capacity, were comprefled in, the following order : Hidrogen, 

 gave water, and two (wine) pints ; oxigen, two pints ; nitrogen, two pints.* 

 probably nitrous jhe refult was, water which bedewed the iniide of the re- 

 ceiver; white floating vapours (probably the gafeous oxide 



• • 

 * Thefe gafes therefore occupied about five times the capacity 

 they were condenfed into. — N. 



of 



