98 ARRANGEMENT OF APPARATUS, ETC. 



parison of failures and successes to eliminate the 

 causes producing the former. 



The following is an example of the form of entry 

 adopted by us : 



Apparatus Horizontal. 



I. Object, coscinodiscu from guano, mounted in 



balsam and bensol equal parts. 



II. Objective, quarter inch, corrected 10° for cover 



glass. 



III. Condenser, two French combinations, together 

 about half an inch in focal length, and distant ^e 

 of an inch from the object. 



IV. Aperture of diaphragm quarter of an inch in 

 diameter. 



V. Lamp 1 3 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 

 bull's 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. 



