824 SUMMARY OF CURRENT RESEARCHES RELATmG TO 



SO that the sides of the spectrum are seen square or upright, thus 



I , not thus / / Adjust the outer tube by means of the rack- 



and-pinion movement E, so that a clear image of the slit K is 

 visible ; regulate the width of the slit by the small milled head L, so 

 that if by daylight the more prominent lines in the solar spectrum 

 are seen. Focus the whole body of the Microscope so that the small 

 lens I just touches the object to be examined. (The small lens 

 merely receives the light from the object and does not form an image 

 of it.) 



If it is desired to register the position of the absorption bands 

 under view, push in the little prism G at the side, turn down the 

 small box H containing the standard scale, and throw the light 

 through it. In the field of the Microscope will be seen on the upper 

 half the spectrum of the object under observation, and on the under 

 half an image of the standard scale as under, Fig. 185. If the small 

 right-angle prism G should require to be cleaned, it must be with- 

 drawn steadily, to avoid chipping. The carrier is made with a pro- 

 jecting prong on one side, which to a great 

 Fig. 185. extent protects the prism ; but such protection 



cannot be put on the other side without stop- 

 ping the light. A piece of black paper has 

 to be cemented on the back of the small prism 

 G, to stop the passage of any direct light. 

 This can be turned up when the prism requires 

 cleaning, which should be done with a delicate 

 piece of wash-leather or cambric handkerchief. 

 If the cylindrical lens F is removed for 

 cleaning, care must be taken in replacing it 

 that the cell is screwed up so that the two 

 marks on the lens are parallel with the slit, otherwise the definition 

 will be impaired. 



'Fase's Zoophyte Trough, Live Box, or Growing Slide.*— This 

 arrangement, devised by the Eev. H. J. Fase, is shown in plan view 

 with the cover removed at Fig. 186, and in transverse vertical section 

 at Fig. 187. A is a glass plate, 3 inches by 2;^ inches, to which is 

 cemented a stout bone or ivory ring B, f -inch in height, having a 

 thin lining of cork C, cemented to it. D is a shorter tube of ivory 

 or bone, with a broad flange at the top, and closed at the bottom by a 

 disk of thin cover-glass E. This tube D slides freely in B. A 

 narrow slot F is cut in the inside of B, from the top outside, sloping 

 to the bottom inside. 



To use the appai'atus as a zoophyte-trough, a ring of indiarubber 

 G, cut through as shown at H in Fig. 186, and of a thickness suitable 

 to the object to be examined, is placed at the bottom of B. The 

 object is placed in this ring with a little water, and the cover is then 

 pressed down gently, any excess of water flowing out of the cut in the 



* Journ. Quek. Micr. Club, vi. (1881) pp. 249-50 (2 figs,). 



