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III. — On some Recent Forms of Camera Lucida. 



By Frank Crisp, LL.B., B.A.. Sec. R.M.S., &c. 



CBead Uth December, 1878.) 



During the present year four or five forms of camera lucida have 

 been brought forward, all claiming to be original, and to enable the 

 observer to see more readily the image of the object and the point of 

 the pencil at the same time, and I have thought it might be in some 

 degree desirable to notice them — as a matter of history, at any rate. 



(1) The first is that of Dr. Hofmann, the well-known optician, 

 of Paris. 



Fig. 1 shows the camera, properly so called, and Fig. 2 its 

 transverse section. 



The rays coming from the object, and passing through the lens 

 C, meet the plate of silvered glass A, by which they are reflected 

 to the transparent glass plate B, and thence to the eye through the 



Fig. 2 {, V 



aperture at E. At D are two lenses of different foci, which can be 

 interposed between the eye and the paper, as with the ordinary 

 Wollaston form. 



With a vertical Microscope the additional piece of apparatus 



