24 PHOTOMICROGRAPHY 



mental, and every care should be taken to select a room 

 as far away from disturbing influences as possible. A 

 basement room is freest from vibrations, and a stone floor 

 less liable to convey them than a wooden one. It is almost 

 impossible to work with any degree of comfort near heavy 

 traffic, running machinery, boilers, or where banging of 

 doors is frequent, unless special precautions are taken 

 to avoid vibrations. 



The bench on which the apparatus is set up must be 

 of the firmest description, and it is often less liable to 

 transmit vibrations if carried on strong brackets attached 

 to the wall, than if placed in the middle of the room. The 

 apparatus itself must also be solidly constructed, and 

 supported on india-rubber pads or several thicknesses of 

 carpet felt. Sufficient rigidity in the microscope and 

 camera is in fact the most effective precaution against 

 vibration, and as a rule nothing further than the rubber 

 or felt pads is required. But if these are insufficient 

 to prevent the communication of movement to the 

 camera, the whole apparatus can be arranged on a stout 

 board or table, and suspended from the ceiling. Suspension 

 is often a space-saving device if the room is high enough to 

 permit of the apparatus being lifted clear by suitable 

 pulleys when not in use. Mr. J. T. Pigg devised a modifi- 

 cation which is, in many cases, even more convenient. He 

 suspends the board carrying the camera and microscope 

 by means of catgut violoncello strings to two iron arches 

 firmly screwed to the table, and sufficiently large for the 

 apparatus to swing beneath them. A special bench in 

 the basement built on masonry foundations, and in- 

 sulated entirely from the building, is the best support for 

 photomicrographic apparatus, when circumstances allow 

 of such an elaborate arrangement. 



