2l8 THE AMEtltCAN MONTttLY [.Tuly 



but simple to use. After dehydration, pour enough over 

 the cover, or lay the whole slide in a bath of oil. It will 

 creep between the glasses in a night usually. Cajeput 

 oil may also be used, but clove oil dissolves tlie celloidin. 

 The sections may be kept in a tightly-closed tube of 

 Canada balsam dissolved rather thinly in xylol, and after- 

 wards mounted in "the usual way in a thicker grade of the 

 same medium. — English Mechanic. 



A Method of Making Type Slides for Opaque Objects with 

 Removable Cover. 



D. BRYCE SCOTT. 



The first step is to prepare the photographed bottom 

 on which the objects are fixed. This can, of course, be 

 prepared to any size or pattern, according to the require- 

 ments of the mounter. For my own purposes I prepare 

 a slide having its surface divided into 300 spaces of vary- 

 ing sizes, which is constructed thus : — 



1. Take a piece of black cardboard 32J inches long 

 and 11|^ inches wide. Scale off 20f inches into 25 divi- 

 sions lengthways, then scale off 6i inches downwards into 

 12 divisions, making the first division downwards the 

 same breadth as the 25 divisions along the top, which 

 will thus become squares. Gradually reduce the size of 

 the remaining divisions downwards, until those in the last 

 line are -only ^ the breadth of those in the top line. Then 

 number the spaces in the corner from 1 to 300. All the 

 lines and figures are to be made with china white dis- 

 solved in water, with sufficient gum added to make the 

 white adhere when dry. Reduce to fin. wide and 2 1-16 

 inches long. The printed photos are next pasted upon 

 ordinary portrait photo cards, and burnished. They are 

 then varnished by pouring a thin filtered solution of 

 shellac over them, and allowing it to dry. Unless this is 



