OF PPIOTOMICROGRAPHIC APPARATUS 49 



of Baker, or the Royal a^d Van Heurck models of Watson. The 

 focussing of the substage condenser should be by a stout pinion of 

 such a length that the hand does not have to grope for it beneath 

 the stage, and should be provided with a good milled head. Fairly 

 stout pinions and milled heads should also be provided for controlling 

 the vertical and transverse movements of the mechanical stage, while 

 the body-tube should be of large diameter to admit the use of low- 

 power objectives required when photographing comparatively large 

 fields. ■ 



Between the years 1889 and 1899, Messrs. Swift and Messrs. Baker 

 produced two very fine photomicrographic cameras that might well 

 to-day rank as standard models for critical high-power work. That 

 made by Messrs. Swift incorporated designs suggested by Mr. Andrew 

 Pringle, and that by Messrs. Baker the ideas of the late Mr. C. Lees 

 Curties — both experienced microscopists and photomicrographers. The 

 essential features of each outfit are very similar, and consist of (1) a 

 long solid baseboard forming a rigid foundation on which the whole 

 apparatus is built; (2) a substantial square-bellows camera travelling 

 on a wide base and capable of considerable extension; and (3) a 

 substantial turntable for the support of the microscope condensers 

 and illuminant. On account of the wide, solid base on which the 

 square-bellows camera travelled, the camera could be extended to its 

 fullest degree and used in that position without fear of vibration 

 during long exposures. With such apparatus the formidable task 

 of obtaining sharp negatives at a magnification of upward of two 

 thousand diameters linear, could be accomplished with certainty, 

 and, given the necessary technical knowledge, celerity and ease. It 

 is no light task to be called upon to produce large numbers of photo- 

 micrographic negatives at such high magnifications, when the work 

 has to be carried out in a house past which heavy street traffic is 

 continually travelling, yet such formed a part of my duties during 

 the terrible years of the war, and was made possible only by the 

 use of apparatus of the design I have just described. Before the 

 work was placed in my hands, attempts had been made to carry it 

 out with photomicrographic apparatus mounted on iron rods, the 

 typical German design; and therefore, of course, supposed to be 

 vastly superior to anything British. The failure was due to no want 

 of skill on the part of the users of the apparatus, but to its inherent 

 faulty design, for it is obvious that vibration will be more readily 

 conducted and its amplitude increased along the rods than through a 

 solid base. Both from long pre-war experience and from the result 

 obtained in that part of my war work just described, I feel that I 

 am fully justified in stating that the right design for photomicro- 

 graphic apparatus intended for critical high-power work is on the 

 lines of the Pringle-Lees Curties models, or the more recent designs 

 of Singer made by Messrs. Watson, and Sons, and of Barnard, made 

 by Messrs. Baker. 



It frequently is necessary to take photomicrographs with the 

 microscope in the vertical position, and here again to employ a camera 

 clamped to an upright iron rod is asking for trouble, to say the least, 

 yet that is the design dear to the heart of the German manufacturer. 

 Many years ago now, Messrs. Watson and Sons placed on the market 

 a vertical model made to the design of the veteran microscopist, the 



