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PROFESSOR W. RAMSAY AND DR, S. YOUNG 
tenths of a degree, and had been frequently tested and indirectly compared with an 
air thermometer. In order to exclude water, the ether was preserved in a stoppered 
tube with a mercury joint above the stopper. 
Fig. 1. 
Three different pieces of apparatus were employed in this research. 
One for the determination of vapour-pressures at low temperatures. The apparatus 
has already been described in the ‘ Philosophical Transactions’ for 1884, p. 37, and an 
improved form in the ‘Journal of the Chemical Society’ for 1885, p. 42. As it was 
impossible to use an india-rubber joint in presence of ether, a tight glass stopcock, 
smeared with slightly deliquesced phosphoric anhydride, was substituted. 
The densities of the saturated and unsaturated vapour at low temperatures were 
