ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



227 



parts ABCR. The fluid is confciined in the glass cylinder R, the 

 floor of which is a glass plate. The plunger and cap are in one piece, 

 C L Pj. Pi is a glass plate, and L an air-hole. The vessel R is filled 

 by unscrewing the cap. For ordinary fluids the plunger is made of metal, 

 but for those with acid reaction or corrosive action, a glass cylinder 

 is substituted. Full directions are given for manipulating the instru- 

 ment and the absorption vessel. 



Zeiss' Hand Spectroscopes.*— These hand spectroscopes are intended 

 for the rapid examination of absorption and emission spectra. They 



Fig. 39. 



allow the whole spectrum to be viewed at a glance, and the slit is 

 symmetrically adjustable. The position of a line is recognised by 

 means of a comparison spectrum, or by a scale of waye-lengths, illu- 

 minated by the source of light. Fig. 39 shows the instrument one- 

 fourth size : here it is seen clamped to a small table T by the piece W ; 

 on the underside of T is a bored-out handle, which serves to rest the 

 apparatus on a pillar. S is the mirror for illuminating the comparison 



Carl Zeiss' Special Catalogue, 1906, pp. 6- 



Q 2 



