ARRANGEMENT OF MICROSCOPE AND CAMERA. 653 
head will answer in place of the extra drum rec- 
ommended for the coarse adjustment. Indeed, 
this drum may be dispensed with in the case of 
the coarse adjustment, if the head of the screw is 
of good size and the movement easy. For the 
fine adjustment, the cord used may be a well- 
waxed linen thread, and for the coarse adjust- 
ment, a piece of fish-line will be suitable. 
This focusing apparatus must be attached 
in a workmanlike manner, and especial care 
must be taken in the placing of the pulleys by 
which the direction of the cords is changed after 
they pass through the board supporting the ap- 
paratus. 
If the photographic apparatus is to be placed 
upon an ordinary table, it should be provided 
with legs placed at the four corners, and it is de- 
sirable that these be of such length as to bring 
the centre of the screen on a level with the opera- 
tor’s eye when he stands erect; for it is more 
convenient and less fatiguing to work in an erect 
position. 
It is evident that this arrangement can be ex- 
tended to any desired extent, by simply using a 
longer board to support the apparatus, and by in- 
troducing a light-proof coupling to connect the 
tube of the microscope with the camera. 
The object of increasing the distance between 
the screen and the microscope is to give greater 
amplification with the same objective. 
It is always desirable to obtain the amplification re- 
quired with the lowest power possible, for the reason that 
