and Laboratory Methods. 



1685 



screws being provided for this purpose. The camera itself is of the ordinary 

 ■" enlarging, copying, and reducing " design. 



The adjustable front or specimen holder has a side shift as well as a rising 

 and falling movement, and is fitted with a series of nested kits from lantern 

 slides up to 8x 10 ; the kits being fitted with spring fingers, so that any trans- 

 parent material, such as ground or opal glass, can be used for mounting a sub- 

 ject to be photographed by transmitted light. 



If photographs by transmitted light are to be taken, and it is found desirable 

 to have the specimen tilted up against the window, the camera and telescopic 

 front can be reversed on the tilting platform, and the camera elevated to any 

 desired angle up to 90 degrees. 

 Cornell Medical College. B. H. BuXTON. 



7 ^ 



B 



:s' 



A' 



ra 



An Improvised Exposure-Test Kit. 



Having no exposure-test kit with our microphotographic apparatus, we recently 

 improvised a form which has served us so well that we feel that a few words 

 concerning it may possibly be of value to some other worker. 



The original kit furnished with the 

 plateholder was about y\ inch thick. 

 A kit frame just fitting into the plate- 

 holder was made by gluing two thin 

 boards, A and A^ (about -^ inch 

 thick), with grooves cut in their inner 

 edges, crosswise to two similar pieces, 

 B and B^. The plate carrier was 

 made from strips about 3y inch wide, 

 and large enough to receive a 4 x 5 

 plate. Thin triangular rests for the 

 plate were glued in each corner. 

 Small pieces of sheet brass driven 

 into the sides of the carrier and moving 

 freely in the grooves in A and A^ serve 

 as guides and allow the carrier a ver- 

 tical movement of about four inches. 

 A brass rod, C, screwed into the top of the carrier and extending through a hole 

 in the top of the plateholder, furnishes a means for adjusting the carrier. A set 

 of interchangeable cardboard screens having horizontal slits of proper width are 

 made to fit into the grooves b b' in B and B^ A set giving, for a single plate, 

 either 3, 5, 9, or 17 exposures respectively has been found convenient. A scale 

 marked on C gives the proper distances of movement. 



If it is desired at any time to use the plateholder with the ordinary kit, the 

 test kit can be easily sprung out at the bottom and removed. We found cigar 

 box wood admirably well adapted for making the kit, since it is well seasoned 

 and of the proper thickness. Burton J. Howard. 



U. S. Dept. of Agri., Bureau of Chem. 



ID 



