1885.] 



MICROSCOPICAL JOURNAL. 



227 



to illuminate the room. Glass of the 

 right color can be obtained from 

 dealers in photographic goods. A 

 less expensive plan is to cover the 



Fig. 36.- Negative Rack. 



window with heav}', translucent, 

 orange-colored envelope paper, which 

 admits a tolerably safe light for de- 

 veloping. Mr. E. C. Pickering has 

 made some experiments upon this 

 subject recently, and has concluded 

 that a material known as golden 

 fabric is the best. Some workers 

 prefer to work by the light of the 

 lantern alone, deeming it more uni- 

 form, and therefore better, than the 

 light from an outside window. When 

 the window of a dark room opens 

 into another apartment, it is a good 

 plan to place the lamp outside of the 

 window, as the room does not then 

 become heated or contaminated by 

 the products of combustion. 



In all cases it is well to test the 

 quality of the light admitted by ex- 

 posing a plate, pardy protected by 

 a strip of opaque paper, to the light, 

 about twelve inches from the window. 

 If after an exposure of fifteen min- 

 utes development fails to show any 

 action of light upon the plate it may 

 be considered the light is of good 

 quality' to work with. 



The light should enter the dark 

 room so as to shine directly upon the 

 plate during development. The op- 

 erator should face the light. 



Running water in the dark room 

 is very desirable. If this cannot be 

 had, a tank should be placed on an 

 elevated shelf with a rubber tube 



leading the water to the place where 

 it is required. The flow of water 

 may be stopped either by a clamp, 

 by bending the tube upon itself at a 

 sharp angle, or by suspending the 

 open end slightly above the level of 

 the source of supply. This is even 

 more convenient than a stop-cock. 



As regards the details of internal 

 arrangements of the dark room, not 

 much can be said, as everything will 

 depend upon the particular circum- 

 stances of each case. The water 

 should be close at hand where the 

 developing is done, so the plate may 

 be flooded with water instantly if ne- 

 cessary. There should be a con- 

 venient shelf or table for plates and 

 holders, a separate shelf for a tray to 

 contain the fixing bath, and a place 

 for chemicals, developing solutions, 

 and sundry bottles that will con- 

 stantly accumulate, and be as con- 

 stantly in demand. 



[To be continued.'] 



Results of Experiments Upon the 

 Adhesiveness of Some Micro- 

 scopical Cements. 



BY PROF. A. B. AUBERT. 



In looking over the literature of 

 microscopy, I have often wondered 

 why no tests have been made of the 

 comparative adhesiveness of the va- 

 rious cements used. Personal expe- 

 rience in the use of cements is un- 

 doubtedly of very great value, never- 

 theless, direct experiment may often 

 be equally useful in deciding what 

 cement to use for a certain purpose. 

 In journals and works on mounting, 

 I found so many more or less con- 

 flicting statements, that I decided, as 

 soon as time permitted, to make some 

 tests with our most common cements. 



For this purpose I chose metallic 

 cells, having an outer diameter of .77 

 of an inch and an inner of .51 of an 

 inch ; thus offering a surface of ad- 

 hesion equal to about .2262 of a square 

 inch. To these cells was soldered a 

 loop of strong brass wire ; they were 

 then attached with the cements to 



