ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



351 



pendently regulated, the regulation for one carbon being performed by 

 the butterfly-nut in the centre of the milled head. Very dark glass 

 windows are placed in the front part of the case, and serve for observing 



Fig. 68. 



Fig. Gy. 



the combustion of the carbons. This front is removal >le for convenience 

 of replachig the carbons. It contains an adjustable tube in whose inner 

 end is fitted a collector of two quartz lenses. The removable filter- 



