24: 



THE AMERICAN MONTHLY 



[February, 



B. Phenol Cg Hg O, . 



B. Anilin C^ H, N, . 



R. Balsam Peru, 



R. Oil of Cassia, 



R. Carbon bisulphide . 



B. Chinolin C9 H^ N 



R. Flint glass 



B. Monobromonaphtalin C^q H, 



Hg I.J + KI in water . 



Methylendiiodide C H, lo 



Stannous chloride 



S in C Sg . 



PinCSg 



Phosphorus* 



Sulphur* . . . . 



Realgar Asg Sg 



Lead Chromate* . 



* Various sources. 



Br 



I -550 

 1.582 



1-593 

 1. 610 

 1.630 

 1-633 

 1-635 

 1.664 



1.742 



1. 7-1. 



1-75 

 2.10 



2.224 



.11 



2.4 

 2.974 



-o- 



Photo-Micrography at the Work- 

 Table. 



BY GEO. A. PIERSOL, M. D. 



It may be stated at once that the 

 simple arrangement here described is 

 offered by no means as a substitute 

 for the usual apparatus for photo- 

 micrography, but only as a very con- 

 venient supplement, which, on re- 

 peated occasions, has proved its 

 value and ready applicabilitv. 



The possession of a light quarter- 

 plate camera suggested its adaptation 

 to the microscope in such a manner 

 that a picture may be made without 

 disturbing in the slightest degree the 

 microscope as arranged for o r d i - 

 nary use — an advantage readily ap- 

 preciated by those engaged in study- 

 ing preparations only temporarily 

 mounted, or objects where change 

 of inclination of the instrument 

 would insure failure. 



To the outer end of the draw-tube 

 is securel}' fastened an adapter bear- 

 ing a thread fitting the photographic 

 lens flange, which, we suppose, is 

 already in the lens-board of the cam- 

 era-front. 



As a preliminary, the detached 

 lens-board should be screwed on to 

 the tube and the latter turned until 

 the board occupies its proper posi- 

 tion in regard to the camera. A 

 mark v^^ill hereafter indicate the 

 proper position of the tube. Now, 

 at any subsequent time in the course 

 of microscopical woi^k, should an 



object present of which a photograph 

 is desired, by simply screwing on 

 the detached lens-board of the little 

 camera and subsequently buttoning 

 this in place on the camera, the ap- 

 paratus is ready without any change 

 having been necessitated. 



Usually the eye-piece will be best 

 removed ; in some cases, however, 

 especially with high powers of imim- 

 peachable definition, the eye-piece 

 may be retained with advantage, as 

 with a short pull the definition is ex- 

 cellent and the light sufficient. With 

 the standard length and large size of 

 tube a field of nearly three inches is 

 readily obtained with a little quarter- 

 plate camera. With the eye-piece 

 retained the entire plate may be al- 

 most covered. 



On beginning work of a character 

 likely to require photographs, the 

 little lens-board may be attached at 

 once, as it is scarcely in the way, and 

 renders the attachment of the cam- 

 era but a moment's work. The 

 short distance between the focussing 

 screw and the adjustments of the mi- 

 croscope being readily within arm's 

 length, no arrangement for focussing 

 is required. 



At first sight it would seem that 

 such a mode of holding the camera 

 would be quite unsteady, but the 

 writer can testify that with a stand of 

 good stabilit)' the little camera is 

 held with such rigiditv that high 

 powers ( ji|j or J, ) may be used with 

 satisfaction. It may be advisable in 

 some instances to place a small rest 

 of wood under the body of the mi- 

 croscope to prevent vibration. 



Regarding illumination for pho- 

 tography, too much pains can 

 scarcely be taken to secure carefully 

 centered and equally distributed light. 

 After many experiments with various 

 condensers — including the Abbe and 

 other wide-angled ones — a b eye- 

 piece, adapted to the substage, has 

 proved to be the most satisfactory 

 with lamp- and calcium-light, and 

 for all ordinary powers it can be 

 strongly recommended as giving a 



