1895.] MICROSCOPICAL JOURNAL. 137 



to be the most easily managed of the three. Only American 

 microscopes were used. 



Focussing Apparatus. — On the right side of the camera 

 two screw eyes are inserted into the base board about 3 feet 

 apart. A hard wood rod 3-4 inch in diameter fits into the 

 space between and is held by two screws passing through the 

 eyes into both ends of the rod. A milled head is attached to 

 the screw at the proximal end of the rod. Two feet of the dis- 

 tal end of the rod are covered with glue and sand dried together. 

 A band of tape goes around the rod and the fine adjustment of 

 the microscope. This afforded a good working adjusting appa- 

 ratus for focus — much better than an assistant working by calls. 



6. Condenser used was a Voigtlander photographic objective: 

 31 inches in diameter and 8 inches long. It is a decidedly first 

 class instrument and in the writer's opinion much of the success 

 obtained was due to this particular instrument. It is costly 

 and valuable ($300)— loaned by Mr. F. W. Hardy A. B., of 

 Bangor, Me. (now of Springfield, Mass.) Compared with other 

 lenses in a large city photographic gallery it excelled them all. 



7. Mirror. — This was made of heavy plate glass 8x8 inches 

 square mounted so as to whirl in two opposite directions. 



8. A Heliostat of simple construction is combined with the 

 apparatus. It has one motion only. 



For use the mirror must be placed towards the north pole and 

 the heliostat mirror in a plane below. 



TIME OF EXPOSURE OF SENSITIVE PLATE. 



One and a half seconds to ten seconds. A piece of black card 

 board 4x10 inches was held in the hand, removed and replaced 

 in the line of light next the slide by the operator or assistant. 

 The length of time of exposure varies with the sun-light and 

 time of day. It is best to time by the action of the proto-sul- 

 phate of iron on the exposed plate. This is a point for the 

 darkroom man's judgment. This description being historical 

 and not dogmatic, only includes the simplest processes which 

 were thought to be the best for the present purpose. They will 

 probably be supplanted by simpler ones in contemplation. 



LIST OF MICRO-PHOTOS. 

 1. Blood of consumptive — human, 3d stage. Wet, l-16th inch objective 



