413 



Note on Ashe's Camera Lucida. 



By D. J. ScouRFiELD, F.K.M.S. 



{Read October I9th, 1900.) 



Some years ago my friend Mr. A. Ashe, a member of this 

 Club, devised a camera lucida for use with the microscope, 

 which he exhibited at one of our meetings in JSTovember or 

 December 1889, but did not bring more definitely to the notice of 

 members. Being convinced that the camera was a really useful 

 piece of apparatus, I had one made according to Mr. Ashe's plan, 

 and with this I have worked ever since. Several others have 

 had similar cameras made, and I believe the results have always 

 given satisfaction. Mr. Ashe has now slightly modified, and 

 thereby improved, his original model, and it has therefore been 

 thought of sufficient interest to bring the matter forward in a 

 more formal way than has hitherto been done. 



As will be seen from the diagram, Mr. Ashe's camera lucida is, 

 in essence, an improved form of Beale's neutral tint reflector, the 

 most important difference being that the light from the eye-piece, 

 instead of being received directly upon the neutral tint glass, is 

 first of all received upon a small mirror which reflects the light 

 down upon the neutral tint and so up to the eye. By this means 

 the light undergoes two reflections before reaching the eye, and 

 the most important defect of Beale's neutral tint reflector, viz. 

 the reversal of tlie top and bottom of the image without a 

 corresponding reversal of the sides, is corrected. 



But the camera now referred to does more than merely correct 

 the partial reversal of the image produced by the simple neutral 



