30 THE MICROSCOPE. Feb- 



The forms are not numerous and are best picked out singly 

 with a mechanical finder, if a reallv clean mount is desired. 



PRACTICAL SUGGESTIONS 



V.y L. A. WILLSON, 



CLKVKLANI), OHIO. 



Photomicrography. — Tlie microscope is placed in a horizon- 

 tid ])Ositioii. The mirror is then vertical, and the tube with the 

 eye-piece is inserted into the camera. Where the tube enters the 

 camera a black cloth is carefully wrapped to exclude all light. 

 Light from an acme lamp is directed upon the concave mirror 

 and reflected from behind upon the object through the tube. 

 A small piece of camphor is placed in the oil of the lamp. In 

 this way. Arachnodiscus has been beautifully taken with a Spen- 

 cer one-sixth immersion objective. With an inch objective, I 

 photographed a Calyptra of a Moss and the Pollinia of Milk 

 Weed and an Ovipositoi" of a Fly with such definition of every 

 minute detail, that no retouching of the picture was necessary. 

 With the one-sixth and exposure of fifteen minutes and with the 

 inch, ten minutes was all that was required.. 



Examining Writing. — Great issues often depend upon the 

 determination as to which of two signatures to a document were 

 first written. The solution of this problem is more difficult than 

 would at first be suspected. The appearance of the lines to a 

 non-expert is frequently the opposite to the truth. Experience 

 and intelligence are requisite to the interpretation of the picture 

 unlolded bv the microscope. Delicate focussing and observing 

 which line first comes into view is one test Try this test by 

 both transmitted and reflected light. Another test is the '' web." 

 The web is formed hy the ink of the last writing, running into 

 the first. This is a very interesting subject to experiment upon. 

 Try it with crossed thick lines and crossed thin lines, thin lines 

 across thick lines and thick lines across thin lines, with the same 

 and with diflerent inks, with slow strokes and quick strokes, and 

 one will be surprised at the intricacy of the problem. 



Photogra^jhy is a good adjunct to the microscope on matters 

 of this kind. First take a negative, from that make a positive 

 then photograph the positive where the lines cross. In the print 



