ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



145 



or weak alcohol, the stand G for it being independent of the rest of 

 the apparatus, which Dr. Fol considers to be essential to prevent the 

 shifting of the object. The objective may be one of Steinheil's 



Fig. 36. 



smallest aplanatics, or a low-power objective provided with a small 

 diaphragm. 



The camera being central, the object is placed at the level of the 

 pivot h, and focused. The camera is then shifted 4^ or 4*5° to the 

 right, and a photograph taken, and then to the same extent on the 

 left and another taken. 



Objectives for Photo-micrography.* — Mr. W. H. Walmsley con- 

 siders that to obtain the very highest results, all powers lower than 



* The Microscope, v. (1885) pp. 219-20. 

 Ser. 2.— Vol. VI. L 



