ARRANGEMENT OP APPARATUS. 109 



parison of failures and successes to eliminate the 

 causes producing the former. 



The following is an example of the form of entry- 

 adopted : 



Apparatus Horizontal. 



I. Object, Polyomatus Argus, mounted in balsam 



and bensol equal parts. 



II. Objective, i inch corrected 10 for cover glass. 



III. Condenser, about quarter inch in focal length, 

 and distant ^tli f an inch from the object. 



IV. Apertura of diaphragm one-eighth of an inch in 

 diameter. 



V. Lamp, 13 inches from stage, edge of flame to- 



wards the object. 



VI. Bull's eye condenser, four inches focal length, 

 four inches from flame of lamp with convex side 

 turned towards object. 



VII. Ground glass of camera, twenty-four inches 

 from object. 



VIII. Focus till the dots appear surrounded by a 

 red areola. 



IX. Sulphate of copper cell placed midway between 

 bulPs eye and substage condenser. 



X. Gelatine dry plate 10 times collodion. 



XI. Exposure, one minute. 



XII. Ferrous oxalate developer, with one drop of 

 bromide solution to the ounce. 



XIII. Result, completely successful, or over or un- 

 der-exposed as case may be, in this case very 

 much over-exposed. 



