Smith, on a Dissecting Microscope. 11 



In tlie first place, the stage, which consists of a stout piece 

 of mahogany, or a plate of brass, is about seven inches long, 

 by five broad — and it is attached to a good firm base, also of 

 mahogany, by four brass or wooden pillars about five inches 

 high (the two front ones being shown in the drawdng), whicli 

 serve the double purpose of supporting the stage, and of 

 giving the requisite elevation to the hand-rests, by means of 

 notches cut in their sides into which the supports fit. These 

 hand rests are about five inches square and one fifth of an 

 inch thick and are fixed to the sides of the stage by hinges, 

 so that they can be placed at any angle required, by means of 

 the supports, which are two pieces of wood or metal fastened 

 to the rests, as shown in the drawings -, these supports are 

 shaped so as not to interfere with the hands in adjusting the 

 mirror, this being one of the points that I have specially kept 

 in view in designing the instrument. 



The other parts more immediately in connection with the 

 stage are the condenser and the arm for holding the magnify- 

 ing lenses ; the former is attached to the front of the stage 

 by a moveable arm in which it slides up and down, and when 

 not in use it can be taken out of the socket and put away in 

 some convenient place ; the horizontal arm carrying the lenses 

 has the usual rack -work and pinion adjustment, and may either 

 slide in and out as figured in the drawing, or also be fitted 

 with a rack- work movement — the arm is turned on one side in 

 order to show a slight bend at the end, holding the glasses, 

 which I think will sometimes be found convenient, when 

 rather a deep trough is being used the sides of which would 

 otherwise prevent the lenses from being brought into focus 

 with the bottom, a circumstance that has in more cases than 

 one proved troublesome to me, as either a lower power had to 

 be used or the subject shifted to a shallower trough. Upon 

 the base of the microscope is a drawer for holding the lenses, 

 knives, and other dissecting instruments, including a small 

 glass syringe, which I find an extremely useful addition to the 

 apparatus. Above the drawer is placed the mirror, which has 

 two sockets, one in the centre for ordinary illumination, and 

 one in the front for oblique light, by which the object under 

 dissection is brilliantly illuminated on a dark ground — a plan 

 in many instances most effective. A very convenient way of 

 doing this would be by putting the mirror upon a socket 

 moving in a groove — so that it could be at once placed in any 

 required position, or when not in use pushed up to the back 

 of the instrument, and thus be altogether out of the way when 

 the space is otherwise needed. 



Drawing No. 2 shows the microscope as it appears with the 



