128 PEACTICAL PHOTO-MICKOGKAPHY 



screen of the camera is by means of rigid rods of wood or metal 

 which are connected together by means of flexible joints (Fig. 

 45) ; there are no cords or similar flexible connections as in the 

 apparatus previously described. A bell-shaped metal cap slips 

 over the fine-adjustment screw and can be clamped on to it. 

 An arm in connection with this clamp goes to a column, adjust- 

 able for height, which is fixed on the table at the side of the 

 triangular bar ; by means of a Hooke's joint a flexible yet 

 rigid connection is made between the focussing-rod which goes 

 to the camera, and the rod connected with the fine-adjustment 

 of the microscope. 



The illuminant supplied with the apparatus consists of 

 an automatic electric-arc lamp. This is enclosed in a well- 

 ventilated box, and there are arrangements for adjusting the 

 position of the crater to the optical axis of the apparatus. The 

 illuminant is not carried on the metal bar, but is simply placed 

 on the table at the end of it ; the collecting-lenses, as well as a 

 water-cooling chamber, are, however, carried on the bar. The 

 camera-base, on its support, is constructed substantially as 

 shown in Fig. 46. As will be seen, it is so designed that either 

 of the component parts of it are adjustable along the metal 

 rods that support it, and can be clamped in any position ; or 

 the whole of the apparatus can be moved to and fro so that it 

 is easy to get at the microscope and to make any adjustment 

 to it. In the later forms of apparatus the displacement of the 

 entire camera is arranged by sliding it on two rollers, so that 

 it can be very quickly and easily altered in position. By means 

 of milled heads at the side of the apparatus it can be firmly 

 clamped in any position when the necessary adjustments have 

 been made. It is almost needless to say that this apparatus 

 in common with all such produced by this firm, is, in point 

 of construction, of the highest class. It must be admitted, 

 however, that from its design it is rather susceptible to 

 the influence of vibration. The camera is stiffly supported 

 so far as its base is concerned ; but as the lateral supports are 

 metal rods, which are not cross-braced in any way, they are 

 specially liable to feel the effect of any tremor imparted to 

 them. At the same time, some of the finest work yet produced 

 has been done with this apparatus ; but it is essential to see that 

 the position in which it is set up is as free as possible from any 



