188 Prof. Rood on the application 
stage be provided with a diaphragm-plate having apertures of 
different size. The mirror should be most carefully adjusted, so 
that the maximum of distinctness in the image on the groun 
correction necessitated by this difference must be asce 
by trial. This can be effected by the use of the fine adjustment, 
(see Shadbolt’s paper). Contrary to some other observers, I have 
found it necessary when using sunlight, with both high and low 
powers, with, and without eye-pieces, to make this correction 
i 
