MEMORANDA. 107 
use in the demonstration of objects to a class of students. It 
is but too well known to those who are engaged in teaching 
how liable the objects exhibited, and sometimes even the 
object-glass itself, are to be injured in the hands of those 
unaccustomed to use the microscope. In oder to avoid this 
risk, Messrs. Murray and Heath have constructed an instru- 
ment intended to combine an ordinary with a demonstrating 
class microscope. It consists of a small microscope, the body 
of which can be inclined at any angle, with a mirror on a 
ball-and-socket joint, and a universal movement to the stage- 
plate. When it is to be used as a class microscope the slide 
is placed in a shallow box, into which it is locked by means 
of akey. The same key locks this box firmly on the stage- 
plate. When the object has been found this latter can be 
secured firmly on the stage in the same manner. After 
focusing, the body is also locked in its place with the same 
key, the final adjustment being made with the eye-piece. 
The body is then placed in a horizontal position, and fastened 
with ascrew. The instrument can now be passed round a 
class-room without possibility of injury either to object or 
object-glass. The illumination can be obtained either by 
holding the instrument against the window or by means of 
a small lamp similar to that employed by Dr. Beale, and 
which can be so adjusted as to be used either for opaque or 
transparent objects. This instrument appears to be very well 
adapted for the purposes for which it is intended, and, at the 
same time, if without the contrivance for locking, to be a 
useful portable form for general or professional purposes. 
