236 now TO WORK 



Wenham dispenses with the use of the ordinary camera, and yet 

 attains its purpose most completely with sundry advantages. He 

 advises a room to be selected having a window or aperture with 

 free access to sunlight. This is closed by a shutter having a hole 

 about 3 inches in diameter ; upon the outside of this aperture is 

 arranged a solar reflector or plane mirror, in such a manner as to 

 be capable of being worked round its centre at the necessary angle, 

 on the outside, by passing the hand through another hole in the 

 shutter to the margin of which a. flexible sleeve is attached. The 

 microscope body is arranged horizontally on a table or bench, so 

 that its axis corresponds to the centre of the aperture. The stage 

 with the object slide clamped on it in proper position, is placed near 

 this aperture on the inside, the light around the stage being shut off 

 by a piece of black cloth. On the bench a vertical stand, consisting 

 of a board with a heavy base, is placed at any desirable distance from 

 the eye-end of the microscope ; this board is supplied with two 

 " under-cut fillets " to hold the sensitised plate when ready. The 

 mirror is first properly arranged so as to throw an equal illumination 

 on the vertical frame-board, a card being previously placed in the 

 exact plane to be occupied by the prepared plate. The image is 

 now focussed on the card. Supposing the operation of exciting the 

 plate to be done in the same room, sufficient light for the purpose is 

 admitted through a small pane of yellow orange non-actinic glass let 

 into the top part of the shutter. When ready the card is removed 

 and placed against the open end of the microscope tube, so as to 

 cut off all light through it, the plate is drained and placed on the 

 vertical frame, the card quickly lifted and replaced against the end 

 of the tube in periods varying, according to the time of exposure 

 necessary, from part of a second to half a minute. The time required 

 will vary according to the quality of the light, the sensibility to it of 

 the collodion or other material used, and the facility with which the 

 actinic rays pass through the object. 



Mr. Wenham enumerates several advantages combined in this 

 method. The length of base-board is limited only by the dimensions 

 of the room. The ease with which any object can be included in a 

 definite space. Facility in focussing a means of so placing the 

 card or sensitised plate at any angle to the axis of the microscope 

 that the surface may be made parallel to objects lying a little out of 

 one plane, and by having a series of paper stops at hand, parts 

 situated in planes, slightly removed from each other, can be focussed 

 and impressed alternately. Then while the first part is being im- 

 pressed, the other part is stopped off, this is then stopped off, the 

 other part focussed and its image allowed to fall in its turn on the 



