ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 825 



the focusiug is completed either by use of the band passing over the pulley at 

 E, or by use of the long rod and fine-adjustment to be described below. The 

 inner tube at D is shown as drawn back in such position as to allow the 

 rays of light to j)ass unobstructed to the screen. 



The camera itself has both bellows and base made in sections, each 

 two feet in length. The sections of the bellows can be readily removed, or 

 additional sections inserted, when greater extension is required. . . . 



The plate and screen-holder is racked back and forth as clearly shown 

 in fig. 



On the side of the base is a graduation in feet, tenths and hundredths of 

 a foot, which enables one to record positions of the screen for producing 

 given magnifications easily. 



The fine motion is communicated to the stage, and not to the objective, 

 as is shown in fig. 227. 



The camera, as shown in the fig., admits of an extension of 8 feet, and 

 sections of base and bellows similar to those above described can be added, 

 extending it almost indefinitely. The extension above given will, however, 

 answer all ordinary demands. 



In its present form the camera takes a 6^ x 8^ plate, and all sizes less 

 than that down to the smallest. 



This apparatus has been specially designed with reference to doing photo- 

 micrographic work of a high character with the greatest possible economy 

 of time. It is for this purpose that the second prism-tube has been added 

 specially for low-power work without the amplifier, and I have no difficulty 

 in making with this camera a half dozen negatives in an evening, when 

 working with lamplight and the amplifier, or from eight to ten in the same 

 time when working with low powers and without the amplifier, in each case 

 doing my own developing. In working by sunlight, where much shorter 

 exposures are required, the same length of time gives an additional amount 

 of work. 



In case one has an extra Microscope, the new apparatus for working the 

 amplifier may be adapted to it at moderate expense, and, by construction of 

 the bellows and extension arrangements as above described, the more 

 important advantages of the camera gained. 



I desire, however, to put myself on record as opposed to the combination 

 instruments — those which are to be used for microscopy ordinarily, but 

 which can be, when one has something worth photographing, for the time 

 being transformed into a camera. The trouble with all such instruments 

 is, they have in general failed to do satisfactory photomicrographic work. 



For rapid work the camera should be placed on a shelf on one side of 

 the room at such a height as to bring the horizontal prism-tubes level with 

 the operator's eye. The position of the camera at one side of the room 

 insures economy of space, and does away with the objection that the camera, 

 even though of considerable size, takes up much room. 



^Vhen it is intended to work by lamplight only it will not matter which 

 side of the room is used for this j)urpose, and the operator may locate the 

 camera to suit his surroundings ; care must be taken, however, to have the 

 graduation of the base on the side away from the wall. If one has plenty 

 of room, the best arrangement would of course be to erect a shelf on horses 

 in the middle of the room, so that the camera is accessible on both sides. 



When it is intended to work by sunlight the camera must of necessity be 

 at either the east or west side of a room with an exposure to the south, or 

 when economy of space is of no importance, it can be conveniently placed 

 in front of a window facing the south, in which may be fitted up the neces- 

 sary arrangements for heliostat, mirrors, or condensing lens. 



