432 HISTORY OF LENSES AND MICROSCOPES [Cn. XII 



Cherubin d'Orleans in 1677 (fig. 250). This, as seen from the picture, 

 is a binocular Keplerian microscope, or rather two of them, as both 

 objectives and oculars are of convex lenses. The objectives needing 

 to be close together makes a divergence of the tubes necessary to get 

 the right pupillary distance for the oculars. In general this form of 

 binocular has been recently revived for dissection, only in the modern 

 form achromatic objectives are used and Huygenian oculars, and by 

 means of prisms the image is made erect. 



Only rather large objects can be studied with such binoculars, and 

 the effort to divide the light from a single objective reached success 

 only as late as 1851, when it was worked out by J. L. Riddell of New 

 Orleans. His description and a figure were published in the Quarterly 

 Journal of Microscopical Science in 1854. From that time on success- 



FIG. 250. BINOCULAR MICROSCOPE OF CHERUBIN D'ORLEANS. 



ful binocular microscopes have been made. The one of Wenham 

 (fig. 52) in England (1860) enjoyed the greatest favor. Tolles in 

 1864-1865 produced his binocular eye-piece, and Nachet, in France, 

 and Zeiss, in Germany, produced binocular instruments, but there were 

 defects inherent in the construction of all forms, especially the defect 

 that they could not be used very satisfactorily with high powers, and 

 they were expensive. Finally, in 1902, Mr. F. E. Ives figured and 

 described a form of binocular suitable for all powers including the 

 nighest oil immersions ( 142, 150). Several recent models have been 

 produced in which the principles he enunciated so clearly have been 

 incorporated (fig. 53, 54, 55). 



In the first binoculars of the Dutch form the tubes were parallel, 

 as with the opera glass, but in many of the later forms (fig. 52, 250) 

 and many others the tubes were made divergent. With others, as 



