459 
1910-11.] Isopiestic Expansibility of Water. 
085 ohm. The plug S, which fitted tightly into the upper end, was made 
of nickel, but was coated with platinum on its under surface. The con- 
centric protecting cylinders N are soldered to the upper copper plate. 
They are insulated from the lower plate by a vulcanite ring G. The 
cylindrical spaces thus separated off from one another by these nickel tubes 
have a width of 2 mm. These narrow chambers prevent the water which 
fills them from circulating too strongly, though the pressure of the water 
is the same as in the rest of the compression-cylinder. This water acts as 
a heat-insulator. The temperature in the heating chamber is measured by a 
Pt. — Pt. Rd. thermoelement, which is enclosed in a thin-walled quartz-glass 
capillary tube and has the form shown by the dotted lines T in fig. 2. 
The Dilatometer. 
As regards the material of the dilatometer several conditions have to be 
satisfied in my experiments. The material must have a high fusing-point 
and otherwise stand temperatures up to 1000° C. Ordinary glass cannot 
