MR. A. E. TCTTTON ON A COMPENSATED INTERFERENCE DILATOMETER, 319 



chamber consists of a wide gun-metal tube, c, very little longer than its diameter, 

 and the cylindrical wall of which is so considerably cut away in three equi-distant 

 parts as to form three relatively large windows separated by three equi-distant 



Fig. 3. 



pillars adequate to maintain rigidity. It is closed at the top by a stout diaphragm, 

 d, whose aperture is filled by a circular glass plate, e, 27 millims. in diameter, which 

 serves the double object of acting as a non-conducting roof to the interference 

 chamber, to prevent upward radiation and consequent loss of heat into the supporting 



