ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 235 
gilded inside (fig. 34) are used. Nickel scales take the place of ivory, 
as they are found not to bulge with changes of temperature. A mirror 
Fig. 32. 
S adjusted by a ball-and-socket joint K allows the light from the lamp 
to be reflected from a mirror L on to the nickel scale B (fig. 35). 
The lamp has also been much improved. For circular apparatus a 
grooved platinum ring has been substituted for the platinum net, 
