28 THE MICROSCOPIST. 



great number of beautiful preparations in minute anatomy, 

 entomology, &c. It consists of a box or case, which is repre- 

 sented by A, Fig. 5. The upper surfaces r, r, are sloped off to 

 form arm-rests. The front of the case (which is not seen in 

 the cut) is furnished with a flap or door, which has hinges at 

 the bottom and a lock at the top ; so that the various parts of 

 the instrument may be packed up inside. 



In the top of the box is a round hole, B, into which fits the 

 short piece of tube atttached to the tin box, C, which is designed 

 to hold the water in which the dissection is made. The ring, 

 D, is the lens-holder, which is adjusted to the proper focus by 

 means of the milled head, E, which moves the rack, F, up and 

 down, working inside the box A. The lens-holder has also a 

 horizontal motion, by means of the rack and pinion, G* Another 

 horizontal motion is produced by a swivel joint attached to F. 

 Inside the box is a mirror, directly under the hole B, so that 

 the light can be directed upwards through any transparent 

 object at B. 



When moderate power only is needed, a simple microscope 

 is the best instrument which can be used ; and for the purpose 

 of making minute dissections it is also the most convenient; 

 but when a very high magnifying power is needed, combined 

 with distinctness of observation, a single (or simple) micro- 

 scope is found to be imperfect : although very small lenses 

 have been made, which magnify exceedingly quite enough 

 for all useful purposes. Good lenses, of a high magnifying 

 power, may be made by drawing out a very narrow strip of 

 glass in the flame of a spirit lamp, and upon the end of the 

 thread thus formed, running a small globule by means of the 

 flame, which may be detached from its thread and placed be- 

 tween two thin plates of metal in which a small hole has been 

 drilled. 



