36 BULLETIN OF THE 



jective as possible, that orthoscopic binocular vision can be obtained 

 both with the simple and the compound microscope. . This discov- 

 ery, together with an account of one method of carrying it out, and 

 a suggestion of the feasibility of other methods, was published by 

 Riddell in the New Orleans Monthly Medical Register for October, 



1852, p. 4, and subsequently in the American Journal of Science 

 and Arts, for January, 1853, p. 68. This article was reprinted in 

 London, in the Quarterly Journal of Microscopical Science for 

 April 1853. (Vol. I, 1853, p. 236.) 



The contrivance described in this first paper was found by Riddell 

 to give orthoscopic binocular vision when used without eye-pieces, 

 but when ordinary eye-pieces were employed a pseudoscopic effect 

 was obtained. This he obviated by the use of erecting eye-pieces ; 

 but, soon after his first paper was published, Riddell devised a 

 second plan, which gave orthoscopic binocular vision with ordinary 

 eye-pieces, and which he subsequently always used for the com- 

 pound microscope, reserving his first plan for the dissecting (simple) 

 microscope. 



A brief notice, containing, however, a correct description of. 

 Riddell's second plan, was published in the New Orleans Monthly 

 Medical Register for April, 1853, (p. 78,) and reprinted in London 

 in the Quarterly Journal of Microscopical Science, Vol. I, 1853, 

 (p. 304.) Subsequently, July 30, 1853, Riddell exhibited a dissect- 

 ing (simple) microscope on his old plan and a compound micro- 

 scope on his new plan to the American Association for the Advance- 

 ment of Science, and read a paper describing those instruments, 

 and pretty fully discussing the principles involved. This paper 

 was published in the Proceedings of the Association, Vol. VII, for 



1853, (p. 16,) and in the New Orleans Medical and Surgical Jour- 

 nal for November, 1853, (p. 321.) It was reprinted in London in 

 the Quarterly Journal of Microscopical Science for January, 1854, 

 Vol. II, (p. 18.) 



Mr. Woodward then related the manner in which Riddell's dis- 

 covery was discussed at the time, in England, by Messrs. Wheat- 

 stone and Wenham, and on the continent by M. M. Harting and 

 Nachet. He showed that Nachet's modification of the compound 

 microscope was suggested by Riddell's first instrument, and that 

 Nachet's excellent binocular dissecting (simple) microscope is, in 

 its optical parts, a literal copy of the binocular dissecting (simple) 

 microscope exhibited by Riddell at the Cleveland meeting in July, 



