MICROSCOPIC OBJECTS. 181 



Description of the Engraving. — a is the eye-piece, b 

 the body, c the arm into which the body screws. This 

 arm and screw are sufficiently stout to carry the body 

 without vibration, and therefore braces are unnecessary. 

 d is the object-glass ; e the triangular gun-metal bar, 

 having a rack cut in its posterior truncated edge. This 

 rack has a pinion worldng into it, the large triple-miUed 

 head of which is represented at/. The stage g has four 

 holes at the comers, either of which wiU receive forceps, 

 condenser, or other apparatus. The centre of the stage 

 has an aperture one inch and a half in diameter, into 

 which fits, by a bayonet-joint, the spring safety shder- 

 holder k. This shder-holder has two moveable plates, so 

 that in experiments with polarized light a plate of selenite 

 inserted between them is not disturbed, while the shder 

 with its object, which rests upon the upper moveable plate, 

 is moved about, h is the stem of the microscope, which 

 can be brought into any position, either vertical, horizon- 

 tal, or inclined at any angle. It wiU also revolve about 

 its axis within the socket r. This latter motion is of 

 great importance, and no microscope defective in this 

 particular can do half the work it ought, j the mirror ; 

 n the pillar, which consists of two tubes, one sliding 

 within the other, by means of which and the tightening 

 ring m the microscope can be raised or lowered at plea- 

 sure. / the sohd tripod foot, which has its two posterior 

 prongs squared so as to fit readily into a cabinet nine 

 inches wide by seven inches deep. The anterior prong 

 of the foot has a hole to receive an arm for cariying a 



