124 A NEW APPARATUS FOR BOYLE'S LAW. 



yond this point, each gas becomes less submissive to 

 pressure — its behavior towards pressure becomes more 

 and more like that of a liquid or a solid. 



These results of Mendeleef are the last words of ex- 

 perimental science in regard to the relation of the 

 volume of a gas to the pressure it sustains. 



As the case now stands, the behavior of a gas under 

 varying pressures may be described as follows : 



There are two degrees of pressure — one considerably 

 above the normal atmospheric pressure, the other con- 

 siderably below it — at which the volume of a given mass 

 of gas varies inversely as the pressure upon it, the ratio 

 being exact. 



Between these two points all gases, except hydrogen, 

 are more compressible than this ratio indicates. 



Outside these limits, whether above the highest or 

 below the lowest, all^gases, without exception, are less 

 compressible than this ratio indicates — the rarefaction 

 of the gas as well as its condensation rendering it less 

 compressible. 



A NEW APPARATUS FOR BOYLE'S LAW. 1 



BY LE ROY C. COOLEY, PH.D. 



This new form of apparatus for experiments on Boyle's 

 law was devised for the following purposes, viz. : 



First, To avoid the necessity of adjusting the volume 

 of the air to the zero of the scale. 



Second, To secure a quick, easy and certain transition 

 from one definite degree of pressure to another. 



Third, To combine in one piece the means of employ - 



1 For descriptions of some recent forms of apparatus for the demonstration of this 

 law, see 



Weinhold's Experimental Physics, by Loewy — p. 240. 

 Science, Vol. 11—284. 



