154 W. Ji. GRAHAM — THE PHOTOGRAPHY OP DIPTERA. 



which ai'e transverse grooved wooden slips to allow a glass plate to be inserted in 

 front of the opening. The easel is clamped to the end of the base-board by a 

 bolt and thumbscrew working in a transverse slot to allow the easel to be moved 

 laterally for centring the picture horizontally on the ground-glass. 



2. The camera. — A square-bellows, half-plate camera, to which a sufficient 

 length of bellows has been added to give an extension of 36 inches. The camera 

 should have a rising front for use in centring the picture vertically. A reversing 

 back is often useful. 



3. The lens. — A Zeiss microplauar lens of 100 mm. equivalent focus. 



4. The filter. — A Wratten and Wainwright's K. III. yellow cemented filter, 

 mounted as a lens-cap. This filter was placed upon the back of the lens, and all 

 focussing was done with it in position. A similarly mounted red filter was 

 occasionally found useful, to increase contrast. 



5. The glass support. — The glass support to hold the object to be photographed 

 was made as follows : — Take a sheet of glass (an old half-plate is suitable) and 

 drill a very small hole through the middle. This hole should be small enough to 

 be completely covered by the thorax of the insects to be photographed. Then 

 cut a piece of cork to fit and cement it into the hole in the glass with Canada 

 balsam in xylol. When the balsam is dry (24 to 48 hours), cut off the pro- 

 jecting cork level with the glass surface, and the support is ready for use. 



6. The milliinetre scale. — This scale is used in ascertaining the magnification of 

 the image on the ground-glass. It is made by cutting off a couple of centimetres 

 from any cardboard scale divided in millimetres. An excellent scale for this 

 purpose will be found inside the cover of Messrs. Burroughs & Wellcome's 

 Medical Diary. The piece of scale selected is cemented to a wooden rod by 

 which it can be fixed above and in the same plane as the insect to be photographed. 



7. The mirrors. — A small square mirror, 5 inches x 5 inches, for use in light- 

 ing the insect from below. An ordinary circular shaving mirror upon its stand, 

 for use in lighting the insect from the side. 



The relative position occupied by these seven parts of the apparatus is shown 

 in the accompanying photographs. 



8. The plates. — Wratten & Wainwright's panchromatic plates were found most 

 satisfactory. The directions for development supplied by the makers were 

 strictly followed. But when the temperature of the dark-room was above 80° F. 

 the plate, after thorough fixing, was removed from the hypo, bath, well washed 

 for 2 or 3 minutes, and then put into a 5 per cent, solution of formalin for 

 5 minutes to prevent frilling. 



9. The stop-clock. — A Welborn Piper's photographer's stop-clock. The de- 

 velopment was carried out in complete darkness, and a stop-clock was therefore 

 necessary. The Welborn Piper clock can be set to strike, after the lapse of any 

 number of seconds or minutes, and was found to be convenient and satisfactory. 



10. Exposure meter. — A Watkins exposure meter of watch form was used, as 

 it could be suspended from the top of the easel alongside the insect where its 

 lighting resembled that of the insect to be photographed. 



