THE PHOTO-MICBOGBAPHIC CAMERA 115 



be made, and replaced again over the microscope at will. It is, 

 however, open to the rather serious objection that the support 

 of the focussing-screen or the dark-slide is at the end farthest 

 away from the tripod, 

 and we have thus 

 very much the same 

 conditions which ob- 

 tain when a metal 

 bar is rigidly sup- 

 ported at one end 

 namely, that the rod 

 is specially subject to 

 any vibration. Such 

 vibration would result 

 in the greatest move- 

 ment of the upper end 

 of the camera, and 

 consequently would 

 have the very worst 

 effects on the defi- 

 nition of the photo- 

 graphs. 



A further develop- 

 ment of the same 

 type is one in which 

 the camera is still 

 carried on a vertical 

 rod, but its base is 

 made so that the 

 microscope can be 

 placed on it (Fig. 38 a). 

 There is also often an 

 additional arrange- 

 ment by which the 



camera can be used in either a vertical or a horizontal 

 position (Fig. 38 b) ; further, it is then supported on a pivot 

 that the camera when used in either position can be easily 

 swung out of the way for the purpose of making any observation. 

 Although this type has a firm base, carrying both camera and 

 microscope, and although the component parts of the apparatus 



