304 Mr. H ALDAN e Gee and Dr. A. Harden on 



piston in the cylindrical tube (T) until the mercury in C 

 has reached a fixed position marked by needle points in the 



B 



Fig. 3- 



vessel C (a.b^c^d?). The pressure required to effect this dimi- 

 nution is read off on the gauge S S. The constants of the 

 instrument were determined by placing distilled water in R, 

 and no allowance was made for the deviation from Boyle's 

 law shown by air saturated with moisture. The results 

 thus obtained with substances such as tin and lead were 

 exceedingly accurate. It was observed that substances 

 which absorb air, such as charcoal, cannot be employed 

 with this instrument. 



