826 SUMMARY OF CUKEENT RESEARCHES RELATING TO 



In any case, the surroundings will decide to some extent just what 

 arrangement will be adopted. 



The following are, so far as I know, the new features embodied in this 

 camera : — 



(1) The application of specific appliances for moving the amplifier back 

 and forth, in order to find by trial, for any given extension of the camera, 

 the best position of the amplifier for projecting the image upon the 

 screen. 



(2) The application of two horizontal prism-tubes, one for use with high 

 powers and the amplifier, and the other for use with low powers without the 

 amplifier. 



(3) The detachable nose-piece and prism-tube for high powers only 

 (fig. 228). 



(4) The cross wires in the diaphragm of the eye-piece of the prism-tube, 

 giving an immediate centering of the object on the camera screen. 



(5) The making of the bellows in sections in such manner as to admit 

 of their easy removal or of a ready indefinite extension. 



(6) The making of the base in sections in combination with the focusing- 

 rod, connected by an automatic coupling. 



(7) The plate-holder, which admits of all sizes of plates, from the 

 maximum of 6^ X 8^ to the smallest, without the use of kits. 



Another new feature, which, however, is not specifically claimed, is this r 

 If one has a prejudice in favour of photographing with an eye-piece, or if, 

 from motives of economy, one desires to dispense with the amplifier and 

 work with the eye-piece, this may be done by simply inserting an eye-piece 

 in the back end of the amplifier-tube. For so working, an adjustable nose- 

 piece for carrying the objective without the high power prism-tube may be 

 furnished, thus dispensing with one of the prism-tubes, which, however, can 

 be added at any time by change of nose-pieces. The object can be still 

 centered by the posterior prism-tube, which is permanently fixed to the body, 

 and the projection of a sharp image upon the screen completed by moving 

 the eye-piece with the pinion E (fig. 228). 



The general claim is made, therefore, that this camera embodies more 

 nearly all the conditions necessary for rapid and successful work than 

 anything heretofore produced. I have no doubt, however, but that a very 

 considerable improvement can still be made, and confidently expect, in view 

 of the great interest now centering in photomicrographic work, that the next 

 few years will develope such improvements." 



It should be added that the author is not unmindful of his obligations 

 to the photomicrographic Microscope of Nachet,* as he says, " The novel 

 point of this camera is the use of the prism-tube somewhat as I have arranged 

 it in my camera, and I very willingly acknowledge my indebtedness to 

 M. Nachet for the suggestion. He has, however, used the tube vertical, and 

 as a fixed part of the apparatus." 



Hartnack's Cupro-ammonia Cell.f — Dr. E. Hartnack has ingeniously 

 modified the form of this cell, so as to enable a thicker or thinner stratum 

 of the blue fluid to be used at pleasure in photomicrography, thus varying 

 the illumination according to the requirements of the particular object. 



The apparatus consists of two ebonite rings, each closed on one side 

 by a parallel plate of glass. The rings slide in one another (hermetically), 

 and when pushed together part of the liquid is forced into a lateral reservoir, 

 from which it is drawn again when the rings are separated. 



* Sec this Journal, 1886, p. 810. t Journ. de Microgr., ix. (1885) p 366. 



