AND RATIO Ol" TIIKIK" ATOMIC \V Kid I ITS. 53 



fusion, exce[>t that tlie tube of infusible glass containini;' the cojuier oxide was 

 joined to the soft glass of the rest of the apparatus by means of ground joints made 

 o-as-tight with paraflin. TIu^ pure dry oxygen issuing from the last drying tube 

 passed to a manometer indieating its pressure, and to a stoix'ock separating tlie 

 a])i>aratus up to this jjoint from that on the other side of the stopcock, where the 

 pressui'e was less until the completion of the process of tilling the globe with 

 oxygen. Beyond the stopcock, a fusil)le metal [ilug closed the tube leading to the 

 globe until the exhaustion was tinished. The tube between tliis sto[)cock and 

 the fusible metal plug was freed from ail' by exhaustion with another pump, after 

 \vdiich the tube leading to this pump was closed by fusion. When the required 

 exhaustion had been obtained, this plug was removed, and the passage of the 

 oxygen to the globe was regidated by a stopcock. Tiie manometer wdiicli showed 

 the pressure of the gas in the voltameter was connected liy so long a tube, and 

 oxvsen was so often blow u out at it, that it was thought impossible for mercurial 

 vapor to mingle with the current of the gas on its way to the globe. 



36. 0XY(iEN BY THIKD MF/niol). MEASUREMENT OF PUESSUIiE. 



The measui-ement of pressure in this series was like that in the iirst series, 

 except ill one particular. In the first series I used wliat Kegnault called a mano- 

 liaroiiietei-, the relation of the tubes in wliich is well known. But in the present 

 case I used a syphon barometer, as shown diagrammatically in Fig. 2'J. In a box 

 stand two tubes, c" and/', one connected to the globe, and the other tilled with 

 mercury by boiling in a vacuum. The upper part of e and the tube/' are in the 

 same perpendicular. The difference of level which measures the pressure of the 

 oxygen in the globe can be accurately and conveniently measured by means of a 

 scale standing in contact with the two tubes and viewed with proper optical 

 apparatus. 



37. oXV(iEN JiY TUIUD METHOD. WEUiHING TilE GLOHKS. 



The globes, after washing and wiping, were hung with their counterpoises in 

 desiccators in the closet under the balance. But the desiccators now used were 

 not required to hold the globes permanently, and were therefore simple boxes of 

 sheet metal, with a cover having holes for the suspension of the globes from the 

 l)alance. The globes were placed in one of these desiccators, the cover was put on, 

 the box was put in position on the rotating platform of the revei'sal mechanism of 

 the balance, and the wires attached to the globes were huug to the auxiliary pans 

 of the reversal appai'atus. Dry air was then admitted at the bottom of the desiccator 

 and there spread horizontally in all directious. This current was introduced 



