450 Prof. Chaltock and Mr. Tyndall on Pressure of the 



Method of the Experiments. 



The hydrogen and its admixture of oxygen were prepared 

 and introduced in the manner described in our paper of 

 1908 (p. 30), the identical apparatus being used for the 

 purpose. As the arrangement of tho discharge-vessels and 

 manometer required considerable alteration they were con- 

 structed afresh. 



Fig. 1 gives a perspective view (diagrammatic) of the new 

 design. 



Fig. 1. 



T is a tilting-table, supported on three points S x S 2 IS 3 , and 

 S 3 is the end of a spherometer screw, on the large divided 

 head of which (not shown) it is possible to estimate a travel 

 of S 3 of 1/40000 inch. 



Upon T is fixed the glass discharge apparatus. The four 

 bulbs M, each 10 cm. in diameter, contain mercury in their 



