1880.] 



MICROSCOPICAL JOURNAL. 



225 



Meanwhile, the very first an- 

 nouncement of Riddell's discovery 

 had attracted considerable attention 

 both in England and on the Conti- 

 nent. Prol. C. Wheatstone, F. R. 

 S., promptly sent to the Microscop- 

 ical Society of London a paper 

 " On the binocular microscope, and 

 on stereoscopic j)ictures of micros- 

 copic objects," which was read 

 April 27, 1853 {Trans., Vol. I, 

 1853, p. 99). This distinguished 

 gentleman, whose investigation of 

 the subject of binocular vision is 

 deservedly famous, had, when he 

 wrote, seen only the reprint " in the 

 last number of the Microscopical 

 Journal^'' {i. e., the number for 

 April, 1853), of Riddell's paper in 

 the America7i Journal of Science 

 and Arts for January, 1853. 

 He stated that he had himself long 

 been convinced "that a binocular 

 microscope would possess great ad- 

 vantages over the present monocular 

 instrument;" and that, shortly 

 after the publication of his first 

 memoir on binocular vision in the 

 Philosophical Transactions for 1838, 

 he had " called the attention both 

 of Mr. Ross and Mr. Powell to this 

 subject, and strongly recommended 

 them to make an instrument to 

 realize the anticipated effect ; their 

 occupations, however, prevented 

 either of these artists from taking 

 the matter up." He further re- 

 marked : " The year before last, 

 previous to the publication of my 

 second memoir, I again urged Mr. 

 Ross, and subseque'ntly Mr. Beck, 

 to attempt its construction, and for 

 a short time they interested them- 

 selves in the matter, but ultimately 

 relinquished it for want of time, 

 and in my opinion over-estimating 

 the difficulties of the undertaking." 

 He then briefly announces Riddell's 

 success, adding: "The method Mr. 

 Riddell employs is similar to the 

 one I recommended to Mr. Beck." 



After having thus claimed for 

 himself the merit of Riddell's dis- 

 covery, he endeavored to detract 

 from its importance, remarking that 

 " A binocular microscope is, how- 

 ever, by no means a novelty, and 

 its invention dates nearly two cen- 

 turies back," giving in substan- 

 tiation of this statement an account 

 of the double microscope of Cheru- 

 bin, (167Y,) to which I shall again 

 refer further on. Subsequently he 

 discussed the question of the pro- 

 duction of pseudoscopic effects with 

 the binocular microscope, and ob- 

 served : " The pseudoscopic effects 

 when inverted images are presented, 

 and the natural appearances when 

 erecting eye-pieces are employed, 

 have not escaped the observation of 

 Mr. Riddell." Pie did not of course 

 know that when he wrote, Riddell 

 had already perfected a method for 

 overcoming this difficulty without 

 " the use of erecting eye-pieces ; " 

 and such a possibility does not ap- 

 pear to have occurred to him. 



Following close upon the com- 

 munication of Prof. Wheatstone, a 

 paper " On the application of bin- 

 ocular vision to tiie microscope " 

 was read to the Microscopical So- 

 ciety of London by Mr. F. H. Wen- 

 ham, May 25th, 1853, {Trans., Vol. 

 II, 1854, p. 1.) Mr. Wenham cites 

 the same -paper of Riddell's that 

 had arrested the attention of Wheat- 

 stone. He had of course been un- 

 able to see Riddell's instrument, 

 but reports that he had carefully 

 tried to reproduce it from the de- 

 scription, " and find that the prisms 

 alter the chromatic correction of 

 the object-glass, and also materially 

 injure the definition." Not only 

 did Mr. Wenham*, according to his 

 own account, fail to satisfy himself 

 in his attempt to copy Riddel's ori- 

 ginal plan, but several modifications 

 which he himself devised were 

 tried " with no good result." On 



