On the Densities of Oxygen and Hydrogen, and on the 

 Ratio of their Atomic Weights. 



By Edward W. Morley. 



PAllT I.— ON THE DENSITY OF OXYGEN. 



I . INTRODUCTION. 



The Urst part of this paper describes three sei'ies of detei-minatious of the 

 density of oxygen. In the first sei'ies, the pressure and temperature of the 

 gas to be weighed were determined with mercurial thermometers and a raano- 

 barometer. In the second series, pi-essui-e and temperature were not determined for 

 each expei'imeut, but were made equal to the pressure and temperature of a stand- 

 ard volume of hydrogen, the comparison being made by means of a differential 

 manometer. In the third series, the temperatui-e was that of melting ice, so that 

 the mano-barometer alone was observed. 



In the first series, the surfaces of the globes in which the oxygen was weighed 

 were hardly touched during the manipulation ; and not touched at all in the second 

 series. In the third series, the globes were in contact with cold water for a con- 

 siderable time. The stopcocks were covered with rubber capsules during this ex- 

 posure, but it seems that this pi-otection did not much lessen the uncertainty 

 usually noticed in the weight of glass so exposed. 



In the reduction of each observation of the first sei'ies, account Avas taken of : 



1 . The expansion of the glass of the globes ; 



2. The errors of the two mercurial thermometers ; 



3. The deviation of the mercurial thermometer from the hydrogen air- 

 thermometer ; 



■4. The difference between the coefficients of expansion of hydrogen and of 



oxygen ; 



