PHOTOGRAPHY OF BACTERIA. 159 



A hinged end- piece is also to be turned out to increase the base upon 

 which the whole apparatus will stand when raised to the vertical. 

 The two-legged support at the opposite end of the apparatus is 

 next worked down by a quick thread screw, and on raising the 

 apparatus to the vertical, the two-legged support drops to the 

 ground, and assists in maintaining the stability of the whole. If 

 it is thought necessary, a simple means can be readily devised for 

 clamping the apparatus, in either position, to the wall of the room, 

 so as to eliminate as much as possible all chances of vibration. A 

 second quick thread screw moves the base -board upon which the 

 , camera and central shding-board are uiounted, so that the camera, 

 iiiicroscope and lantern can be raised to a convenient height from 

 the ground. 



The various parts of this apparatus, may be described in 

 detail. 



The Microscope and its Attachments. — It is most essential that 

 the micx'oscope should be perfectly steady. The microscope was made 

 by Zeiss, and to ensure steadiness, the horse-shoe footpiece fits under 

 a projecting ledge, and is then clamped by a cross-piece, so that 

 it is- firmly fixed. 



The microscope with the means for clamping it and the oxy- 

 hydrogen lantern are carried upon an independent sliding-board, 

 which admits of movement to or from the camera. The sUding- board 

 also moves upon a centre, which enables the microscope to be turned 

 out from the median line ; in fact, to be turned at a right angle to the 

 position it occupies when ready for the exposure. The object of this 

 contrivance is to enable the operator to sit down by the side of the 

 apparatus, and with comfort to arrange the object in the field of the 

 microscope. On turning the microscope back into the median line, it 

 is fixed in the optical axis of the apparatus by means of a suitable 

 stop. The sUding-board is provided with a small grooved wheel 

 receiving an endless cord, made of silk or fishing-line, which passes 

 round the grooved, milled head of the fine adjustment of the 

 microscope. When the slidmg-board is returned to the median 

 line of the apparatus, the milled wheel connected with the fine 

 adjustment impinges upon the wheel of the long focussing rod. 

 The latter is provided with an india-rubber tire, which grips the 

 teeth of the milled wheel, and thus the long focussing rod is placed 

 in connection with the fine adjustment of the microscope. 



Illwmination. — The oxy-hydrogen lamp has been more frequently 

 employed by the author than the paraiiine lamp, partly on account 

 of the diminished time in exposure, especially when em.ploying very 



