THE SIMPLE MICROSCOPE. 



53 



arm, /, nine inches long, provided at its free end, a, with a 

 stout ring, ff, into which either a compound body may be 

 screwed, as seen in fig. 32, or a lens, ^, set in a large cell 



may drop. The com- 

 pound body, it will 

 be seen, has also a 

 rack and pinion mo- 

 tion of one inch in 

 extent for a fine ad- 

 justment, and the 

 body itself may be 

 inclined at any angle 

 by means of a swivel 

 joint to the ring. 

 This instrument is 

 particularly useM for 

 minute dissections 

 carried on in large 

 troughs imder water; 

 and when the opera- 

 tor wishes to view 

 his dissection with a 



Fig. 32. 



high power, he may remove the single lens under which 

 he has been at work, and substitute for it the compound 

 body, which is usually supplied with three eye-pieces, and 

 an inch and two inch object-glass; but in no case is he 

 required to move his dissection, as the compound body can 

 be appKed to the same objects as the single lens. To make 

 this instrument available for the general purposes of a com- 

 pound microscope, it is provided with an oblong frame or 

 box, open at the sides, and in the bottom of which is con- 

 tained a mirror; the top of a box having a hole in it 

 about an inch and a half in diameter, answers the purpose of 

 a stage, and into it a pair of forceps, a frog plate, and other 

 apparatus may be fitted, as into the stage of an ordinary 

 compound microscope. To the ring, also, may be adapted a 

 small arm, capable of carrying a Coddington or other lens of 

 high power. 



