68 



DRS. J. A. MARKER AND P. CHAPPUIS ON A 



Fig. lii Fig. 13. 



Sketch of Gas Thermometer. 



The reservoir is shown raised above its natural 

 position in the comparison bath, and the screens 

 are all removed. 



/?, mercury reservoir; a, steel connecting tube; 

 r, r, scale ; r. and v, slide and worm gear hold- 

 ing the barometer and scale ; m, m, handles for 

 adjustment of position of barometer and scale. 



Detail of Manometer-point. 

 I, glass tube optically ground inside 

 and out; b, brass collar, holding 

 the cylindrical stopper of nickel- 

 steel ; v, ground joint. 



Fig. 14. 



Section of slide carrying the mano- 

 meter and scale. 



Fig. 15. 



1.1. 



Zero apparatus. 



