2 JOHN JOHNSTON AND L. H. ADAMS 



sandstone, 2 cm. in thickness, in spite of a certain excess counter 

 pressure of steam; his apparatus is represented^ schematically in 

 Fig. I. A disk of Strasburg sandstone was clamped between two 

 chambers, the upper one (L), open at the top, containing water, the 

 lower one (F), gas-tight and connected to a stop-cock (C) and 

 manometer (M). The whole rested on carbon blocks, and was 



Fig. I. — -DiagTam to illustrate the form of apparatus used by Daubree 



placed inside a loosely-closed metal box heated from beneath. 

 Daubree caused the temperature in the inside of the box (as 

 measured by the thermometer T) to remain for some time at 

 160°, the cock C being open meanwhile. Upon closing C he 

 observed that the mercury column rose gradually to a height of 

 68 cm. (0.9 atm.). On relieving the pressure by opening C, and 

 subsequently closing it again, he observed the same effect again. 



' See Daubree, Geologic experimentale, Paris, 1879, P- 238. 



