997 



copper chamber U, after tlie thermometer having been attached toils 

 support. (See fig. 1 and 4). On tlie level of the adjustment-space it is 

 provided with a slit for illumination and one for reading u, (see fig. 4). The 

 former is closed by a piece of ordinary glass. The reading-slit is provided 

 with a slide holding a thin plan-parallel piece of glass. The rising 



