1898-99.] On Obtaining a Large Field of View, &e. 57 
and thus slightly lengthening the draw-tube. In this way the 
field of view may be anything between five-eighths of an inch 
and 1} inch. As the object-glass referred to is constructed 
for a 10-inch tube, it may be objected to its use in the above 
way that the definition would be affected by reducing the 
length of tube; but it has to be kept in view that by shorten- 
ing the tube the magnification is very much reduced, and the 
objection may be held in this view to be out of court. It will 
be seen from the above that no adventitious aid is required to 
Photo-micrograph of crown piece. 
obtain the object in view—just the ordinary object-glass and 
eyepiece. It has been shown to the Society to be capable of 
being used in photography, as the photograph of the crown 
piece handed to the members demonstrated. — It is necessary, 
when using the microscope in this way, to use the very best 
object-glasses ; no second-rate ones will do, The low powers 
made by Mr Wray have been found among all others to possess 
the very highest qualities, They have the largest possible 
lenses, and thus admit much light, coupled with extremely fine 
definition, Great stress is laid upon the use of the low-power 
