122 ARRANGEMENT OF APPARATUS. 



objective. The apparatus is considered as still re- 

 maining in the position adopted in our first ex- 

 periment. 



The lamp stand, and bull's eye condenser, are 

 clamped in their original position by binding screws 

 fitting in the division running down the centre of 

 plank no. 3. 



The camera legs are shortened to allow of the 

 upright division no. 1 and no. 2 assuming the hori- 

 zontal position, but need not be removed (they are 

 omitted in the figure). The side board is detached, 

 and replaced two bolts lower down. When firmly 

 screwed on, it keeps all three division of the plank 

 perfectly rigid, and in a straight line with each other. 



The camera and sulphate of copper cell are re- 

 moved; Swan's incandescent lamp substituted for 

 the parafin, the edges of the carbon filament being 

 turned towards the microscope. 



Connection is now made with the source from 

 which the electricity is supplied. We shall here 

 only mention that dynamos are preferable to a 

 battery, but unfortunately the great expenditure 

 necessary for their maintenance, as well as first pur- 

 chase, puts their application to photographic pur- 

 poses beyond the reach of ordinary individuals. In 

 a late number of the Photographic News an electric 

 generator worked by hand is proposed, which may 

 prove practicable if sufficiently low in price. 



If battery power is used, thirty cells of Grove's 

 battery will be found sufficient for a full sized Swan's 

 lamp. We have had no experience of the smaller 



