176 PKACTICAL PHOTO-MICEOGKAPHY 



the greatest heat of summer and the low temperatures of winter. 

 Certainly a room with a northern aspect would be better suited 

 than any other. 



It is likely, however, that the majority of workers will to a 

 large extent have this point determined for them, and may 

 have to devote a room to the work which is not required for 

 other purposes. It therefore becomes necessary to point out 

 such methods as are available for overcoming the troubles 

 due to vibrations, such as more particularly affect the 

 upper part of a house. It is by no means certain that any 

 apparatus is better for being very firmly fastened down to the 

 floor, unless that floor is of particularly solid construction, 

 or as in the writer's case, where in the course of building 

 the house a steel girder was placed in the floor in the 

 position which the apparatus was to occupy. Obviously this is 

 a refinement that can rarely under ordinary circumstances be 

 obtained ; and, where an ordinary floor is the only means of 

 support, then some method of reducing the transmission of 

 vibrations may be necessary. 



The simplest and most easily applied is to place under the feet 

 of the apparatus three- or four-inch cubes of solid india-rubber. 

 This reduces the smaller tremors, and effectually prevents 

 any but a definite shock from being transmitted. A more 

 drastic although somewhat more troublesome method, is to 

 sling the whole arrangement on stout cords. The illustration 

 (Fig. 61) shows a method of carrying a small apparatus on this 

 principle as suggested by Mr. J. I. Pigg. In this case the 

 camera and microscope are supported on onp board, which is 

 slung between two metal uprights, themselves standing on an 

 ordinary table. This arrangement is very efficient indeed where 

 work has to be done in an ordinary room, and it will need to be 

 fairly severe vibration that will affect the resulting photographs. 



If the camera is of a larger type, it will hardly be possible 

 to so hang it. In most cases where the weight is considerable 

 it is better, if possible, to let the cords be hung from beams in 

 the ceiling ; in this case much better isolation from movements 

 of the floor, due to persons moving about in neighbouring 

 apartments, is obtained. 



In extreme cases thick india-rubber cords may be substituted 

 for the ordinary cord. 



