506 SUMMARY OF CURRENT RESEARCHES 



used it in the same way. The following notes relate to a piece of appa- 

 ratus which has been gradually developed during several years, and 

 which has as its object the application of the ordinary Microscope 

 camera lucida to the purposes we have mentioned. It is a piece of 

 apparatus which in use is placed in front of a window, in fact, is usually 

 attached either to the window, the window casing, or to special uprights 

 near by. As exemplified in this laboratory, the apparatus is attached to 

 two upright girders, the same two that carry the ordinary photographic 

 camera. Both these attachments are slung on sash weights, and can be 

 moved up and down, so that either may be brought into play while the 

 other is raised out of the way. The camera lucida attachment consists 

 of two distinct frames, which are separated near the middle of the win- 

 dow by a distance of 8-10 in. The left-hand frame is designed mainly 

 to support the camera lucida ; the right-hand frame to support the 

 drawing board. Both frames carry adjustable brackets, and each bracket 

 carries a horizontal shelf. The left-hand frame, therefore, has a hori- 

 zontal shelf carrying the Microscopes, and this shelf is adjustable in the 

 vertical direction, and can be clamped in any desired position. In a 

 similar manner, the right-hand frame carries a horizontal shelf, or 

 drawing board, also adjustable in the vertical direction. The drawing 

 board presents the peculiarity of being also adjustable in the horizontal 

 direction, and of rotating about a horizontal axis so as to pass the 

 opposite shelf — it is required sometimes above that shelf and sometime& 

 below it. The size of the apparatus is determined by that of the human 

 body. The greatest distance that can be comfortably reached by an 

 ordinary artist for drawing purposes is about 30 in. — i.e. when gazing 

 through the camera lucida he cannot comfortably produce a drawing 

 at a distance of more than 30 in. from his eye as the light travels. 

 The camera lucida is usually carried on a piece of tubing clamped 



Explanation op Fig. 62. 



Sketch of the arrangement of a camera lucida for the production of drawings 

 of objects at nearly the natural size. The apparatus is attached to upright steel 

 girders, one at each side of a window. The artist faces the light. 



1, 2, the two steel girders, which are imbedded in several tons of cement beneath 

 the building, and pass through the floor without contact ; 3, cross-piece to carry 

 an ordinary camera 4, this cross-piece being hung on sash-weights, and sliding 

 in the vertical direction and readily clamped by the side screws shown ; 4, ordinary 

 camera pushed up out of the way, but easily brought into use, as shown in fig. 60 ; 

 5, anti-friction arms of the cross-piece 3, which roll against the edges of the 

 girders 1,2; 6, left-hand box of roller blinds ; 7, right-hand box of roller blinds ; 

 8, light-tight vertically acting roller blind of the window ; 9, 10, horizontally act- 

 ing roller blinds from the boxes 6, 7 ; 11, object to be drawn, held in stage forceps ; 

 12, mirror of ordinary camera-lucida ; 13, horizontal stage, adjustable in the ver- 

 tical direction, designed to support the object 11, which in this case is supported 

 on the stage of a Microscope carrying no objective or eye-piece ; 14, horizontal 

 stage, adjustable in the vertical direction, designed to support the drawing board, 

 which tips out to pass 13, and is also adjustable in the horizontal direction ; 15, 16, 

 framework supporting all the apparatus 6-14, and slung on sash-weights so as to 

 be easily pushed up out of the way when the window is used for other purposes ; 

 17, screw clamp to stage 14 ; 18, roller blind acting as a light trap and diaphragm, 

 when the window is used with the solar projector, as shown in fig. 61. 



