THE CAMERA, ETC. 45 



A board three feet long, two and a half inches 

 wide, and one inch thick, B fig. 24, has six holes 

 drilled in it, six inches apart, the last holes on either 

 side being three inches from its extremities. This 

 enables it to be screwed on to any six bolts at the 

 same time, thus keeping the several parts of the 

 beam steady, in the various positions we are com- 

 pelled to place it, owing to the different methods 

 adopted to meet the requirements of every case. 



The first division of the beam I, fig. 24, is intended 

 to support the oblong board to which the camera 

 is fastened; a binding screw and a brass slip 

 working in a slot cut down the centre of the 

 beam attaches them to each other. 



On the second division, 2, a platform of sufficient 

 height to enable the microscope to be adjusted to 

 the camera is erected, the microscope being pre- 

 viously firmly attached to a separate board, sliding 

 to and from the lamp, between two grooved slips on 

 the top of the platform. This should also be 

 clamped in position by a binding screw. 



Owing to the different forms of microscope stands 

 it is ^mpossible to adhere to any fixed rule with 

 regard to the method of attaching the microscope to 

 the platform. It must, however, be as accurately 

 and firmly fastened as possible, while its motion to 

 and from the lamp must take place without disturb- 

 ing the centring of the different instruments. 



A thick board the same width as the stand and 

 about twelve or fourteen inches long, is fastened at 

 right angles to plank No. 3 on the extremity behind 



