364 THE president's address. 



been the influence of the spectre that it is deemed necessary to 

 have heavy metal beds for these microscopes, for the purpose 

 of strutting up the end of the crane arm ; this, together with 

 draw-tube and eye-piece clamps, is thought to be the correct 

 design for a photomicrographic instrument. We now come 

 to the funny part of the design in the class of apparatus 

 referred to, for when all this hypercritical care is taken to 

 make the instrument as rigid as a solid block of metal, the 

 wooden base is cut and the whole put on a pivot. Even grant- 

 ing that a pivot is necessary, it is the camera with its base 

 board that should be turned aside, the microscope being left 

 unmoved on a firm trestle, which arrangement was invented 

 some time back, and is still used. 



The vibration scare is in a great measure due to the neglect 

 of the re-examination of the image after the photograph has 

 been taken; if that had been done it would be found that the 

 loss of the negative was due to an alteration in focus, and not 

 to vibration. 



We will now take the second point, viz., the non-fixity of the 

 camera. With some the camera evidently appears to be the 

 end all, and the be all, of the apparatus, it is consequently fixed, 

 and every adjustment, from the source of light to the eye- 

 piece, has to be centred to its axis. But really the camera is 

 the most unimportant part of the whole apparatus, for it can 

 be entirely dispensed with ; the late Dr. Woodward, for ex- 

 ample, did not use one. The rule is, never mind where you 

 project your image, but wherever it happens to come there 

 place your plate. The things of primal importance are the 

 obtaining of a visually critical image, and the correct projection 

 of that image, but the exact position of that image has no 

 importance. Mr. Bousfield has felt the intolerable nuisance of 

 a fixed camera, so he has put traversing motions to the back of 

 it to compensate for its fixation. Obviously, however, the non- 

 fixity of the camera is the simplest way out of the difficulty, not 

 to mention some other advantages it has. It must be mentioned 

 that I have designed photomicrographic apparatus with fixed 

 cameras, but then the end in view was cheapness (30/-), the move- 

 ability of the camera being sacrificed to that end. Bellows are, 

 to my idea, not suitable for photomicrographic work, because a 

 perfect apparatus must be capable of extension from six inches 



