THE COMPOUND MICROSCOPE. 93 



down of the body, L, in the outer tube, I, forms a very good 

 coarse adjustment, whilst, after the object-glass has been 

 brought sufficiently near the object by this means, the fine 

 will answer for the remainder. The height of this instru- 

 ment, when the compound body and draw-tube are shut 

 down, is not more than eight inches, and it is not much too 

 large to be carried in the coat pocket. With all these micro- 

 scopes the usual accessory instruments are snppHed if re- 

 quired ; many of them differ in some points of construction 

 from those both of Messrs. Powell and Ross, and with them 

 wiU be fully described in the chapter devoted especially to 

 the consideration of these subjects. 



Before concluding this chapter, the author would direct the 

 attention of his readers to the compound microscopes of Mr. 

 Pritchard, fully described in the last edition of his Microscopic 

 Illustrations, where will also be found full directions for the 

 construction of proper stands, and the methods of using the 

 various microscopes and the pieces of apparatus supplied with 

 them, with numerous illustrations to explain the same, aU of 

 which subjects wiU repay an attentive perusal. 



A compound microscope constructed by Mr. Varley, and 

 described by him in the fifty-fifth volume of the Trans- 

 actions of the Society of Arts, as the Single Lever Microscope, 

 here also requires especial notice. This instrument is repre- 

 sented by fig. 47, one-third of the real size, and consists of a 

 hollow foot, somewhat like that of a bird in shape, from 

 which a stout pillar rises, having at its top a thick, flat disc 

 of brass, a, with a central hole; to this the microscope is 

 joined by means of a strong block, b, whose face is turned to 

 fit against it ; a central screw passes through the hole, and all 

 the important parts of the instrument are kept fast to the 

 block by the screw nut, c. Through the block, h, slides the 

 long rod, d, against which a saddle is placed for the screw, e, 

 to bind it fast at any height. To the same block, b, the back 

 plate of the stage, g, is fastened; from this is given off the 

 arm, r, which, in connection with the shorter arms, q q, sup- 

 ports the fulcrum of the lever, s, having attached to it two 

 balls, the lower one of which works between two plates at p, 



