28 THE AMERICAN MONTHLY [Jan 



Methods Unscientific. — "I think Prof. Gates has rushed 

 into print too soon with his expectations based upon some 

 very crude experiments. He discards expensive, high 

 grade lenses and obtains better results with two micro- 

 scopes in tandem, fitted with any old thing's for objectives. 

 To prove his point he exhibits a confessedly 'bad' photo- 

 graph. At length surmising that the ordinary objectives 

 are not bearing the strain very well he has ordered spe- 

 cially corrected objectives and some new apparatus, — 

 things which would have been done and the whole tested 

 fully, by a wise experimenter before writing at length 

 and drawing on his imagination. Any distinct advance on 

 these lines will be through the aid of specially corrected 

 objectives of the highest grade, and much very expensive 

 apparatus, and the whole promises to be a very unwieldy 

 laboratory instrument projecting an 'invisible image.' 

 There is nothing better in sight, at the present outlook, 

 than the 'expensive' but handy homogeneous immersion 

 objective which projects a visible image." — S. G. Shanks. 



MICROSCOPICAL APPARATUS. 



Ohmann-Dumesnil's Camera. — It must be capable of 

 drawing out quite a distance to get amplification. Hence a 

 bellows is absolutely required. At a photographer's sup- 

 ply house, an old second hand camera can usually be got for 

 a dollar. The box with bellows is thus provided cheaply. 

 The box opening should be about 8 x 10 inches. Then 

 procure a truncated four-sided pyramid of tin whose base 

 is the size of the front frame of the camera and whose 

 smaller end is 3 inches square. Its height, about 10 inches. 

 Any tinner should make this for 50 cents. In a piece of 

 wood % inch thick, bore a hole in the centre, of diameter 

 the same as that of the microscope tube and close the 

 small end of the tin with it. Secure the other end of the 

 tin extension to the front of the camera. Paint the tin a 

 dull black inside and outside as well. Cover the edge of 

 the round aperture in front with velvet so as to secure a 



