-turnLl"'.WuT«'/a'] NOTES AND MEMORANDA. 207 



individual specimens of tlie same species, among natural objects. The 

 test-plate used was one of Nobert's later make, containing nineteen 

 bands, the last of which, or the nineteenth baud, was composed of lines so 

 fine and close that it requires over 112,000 to occupy the space of one 

 inch. These were clearly resolved by direct* light illumination from 

 a kerosene lamp, with the one-tenth immersion objective f and a B eye- 

 piece. Among those invited who witnessed this performance may be 

 named Professor Wolcott Gibbs and Dr. B. A. Gould of Cambridge. 

 The true lines of this nineteenth band have never yet been seen by 

 Nobert himself, and their resolution has been pronounced both by him 

 and many European microscopists of eminence as physically impossible. 

 We cannot learn that anyone in Europe claims to have seen them, if we 

 except, perhajis, Nachet of Paris. At the U. S. Army Medical Museum 

 in Washington, D.C., with a one-sixteenth immersion objective, made 

 by Powell and Lealand of London, the sunlight being controlled by a 

 heliostat and rendered monochromatic, excluding all rays of the sjiec- 

 trum except those of the shorter wave-length, and condensed with a 

 one-sixth objective of ToUes' make, the lines in question have been 

 photographed. 



" The one-inch objective on exhibition is constructed for use in water, 

 and seems admirably adapted for tank work where minute dissections 

 are to be performed. The prism arrangement of the one-fourth ob- 

 jective for illuminating ojDaque objects through its anterior combination 

 lens is new and worthy of special consideration. It is simple, its use 

 employed or readily cut off, and is free from the glare and other objec- 

 tions which have rendered nearly useless all former efforts to improve 

 the illumination of opaque objects under high powers. 



" The binocular eye-piece is also the invention of Mr. Tolles. It 

 not only seems to do well what any other form of binocular micro- 

 scope will do, but it is also suitable for use in those cases where all 

 other binoculars fail, their uses being limited to the lower powers in 

 consequence of the relationship of their binocular arrangement to the 

 objective. Mr. Tolles' arrangement connects it with and makes it a 

 part of the eye-piece. It may also be used with telescopes." 



Belgian Prizes open to Microscopists. — Among the prizes offered 

 by the Belgian Academy of Sciences in 1871 are the following : — 



(1) A determination, by new researches, of the position which the 

 genera Lycopodium, Selaginella, Psilotum, Tmesij^teris, and Phyllo- 

 glossum ought to occuijy in the natural series of vegetable families ; 



(2) a description of the mode of Eeproduction in Eels. The prizes 

 will be gold medals, each of the value of 321. (800 francs). The 

 essays are to be written legibly in either Latin, French, or Flemish. 

 The authors of the essays inserted in the reports of the Academy will 

 have the right to 100 copies of their essay free, and as many addi- 

 tional copies as they wish at the rate of four centimes per sheet. The 



* Direct light should not be confounded with centrnl light. The light was 

 direct from the lamp, unmodified ; of course it was very oblique. 



t Tliis is the same instrument referred to by Dr. J.J. Woodward in his paper 

 in 'The American Journal of Science' for September, 1869, and in a communica- 

 tion to the 'Monthly Microscopical Journal,' London, for December, 1869, and 

 called by him an eighth only. 



