io8 PICTURING MIRACLES 



riage, and is in perfect alignment, from the light 

 through the microscopes, to the center of the film, 

 and so made any one of the elements may slide back 

 and forth, be taken off and replaced in the same per- 

 fect alignment. 



The camera must be the very best. If in 35 mm., 

 either a Bell and Howell, or a Mitchell, and very 

 heavily mounted. These cameras have no vibration 

 in their movements, and will carry film up to thirty 

 frames a second without undue wear. 



The Mitchell has the advantage of the lens stay- 

 ing in one position to focus while the camera slides 

 to one side, but it costs about $4,000. The Bell and 

 Howell, costing half that, has a turret head for the 

 lens to revolve in, but that method of focusing is not 

 suitable for microscopic work, so I found it advisable 

 to focus on the aperture, even though I have to look 

 at it diagonally, but with a prism and a magnifying 

 glass, I can work with perfect accuracy. I also have a 

 reflecting prism that stops about 15% of the light; 

 I can watch the subject through it all the time, un- 

 less it is something that requires all the light for a 

 comparatively short time, watching till all is ready, 

 then flipping the prism out of range, taking the pic- 

 ture, and flipping it back to see if all is well. 



In most of my work I use the tandem microscopes, 

 but for extremely high magnifications I use the oil- 



