and Laboratory Methods. 



Fig. 4 a. — Cross section of the metal spe- 

 cimen pan. One-half actual size. The 

 base of the ball and socket joint is too 

 small, it should fill the socket. 



metal rod which extends from the level of 

 the coarse adjustment screws to the upper- 

 most camera support (Fig. 8). The rod is 

 provided with two milled heads which are 

 adjustable upon it. These may be set at 

 any point so as to be within easy reach. 

 At the lower end of the vertical rod is a third bracket which supports a 

 bevel gear, the cogwheels of which are each about o cm. in diameter (Fig. 

 4). The upper wheel is attached to the vertical rod, while the lower has 

 attached to it by means of a Hooke's key an iron rod like that attached to the 

 axis of the pulley wheel, but only 3 cm. in length. When the leveling plate is 



Fig. 5 — Pyncnogonum Stearnsi Ives : "nith egg masses. Exposure 1 minute, otherwise 

 identical with Fig. 6. x 10. 



in position these two iron rods (that attached to the pulley wheels, and that 

 attached to the lower part of the bevel gear) may be united by means of a brass 

 sleeve in which are two screws (Fig. 4). The Hooke's keys give this connection 

 a certain degree of flexibility and so permit of considerable movement of the 

 leveling plate and of adjustment of the pulley wheels on the cross bar. When 

 the connections have been made, the coarse adjustment of the microscope may 

 be manipulated by an operator looking at the ground glass of the fully extended 

 camera. 



A direct connection might of course be made between the vertical rod and 

 the coarse adjustment of the microscope, without the intervening pulleys and 

 cords. In focusing there is some risk that the microscope tube may be brought 

 against the lower end of the camera. If this happens the cords slip and no harm 



