ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 301 



band, from " 120,000 " upward. No objection was mado to this form of 

 acceptance. 



At an appointed time, one afternoon, tbe Microscope was placed in 

 a wooden cabinet which nearly excluded daylight, and light from a 

 kerosene lamp, with a large fiat wick, placed edgewise at a distance of 

 about two feet, was admitted through an opening in a cabinet on a level 

 with the nose-piece of the Microscope. The stand was a large and 

 heavy one, made by Mr. Fasoldt himself, with about ten inches of tube- 

 length, including the objective, and furnished with a Bausch and Lomb 

 1/12-inch hom.-imm. objective claiming 1'40 N.A., and a 1-inch "peri- 

 scopic " ocular by the same makers. The illuminating rays were brought 

 to a focus at the side of the nose-piece, and about one-fourth of an inch 

 from it, by means of a " watchmaker's glass " of about two inches focus, 

 mounted as a bull's-eye condenser, the best effect being gained with an 

 achromatic one said to have been made for the purpose. The divergent 

 pencil was then admitted to the tube, and reflected downward through 

 the objective by means of a cover-glass internal illuminator claimed and 

 patented by Mr. Fasoldt as his own. The peculiarity of this illuminator 

 (aside from the oddity of its large size and square shape, the substitution 

 of Fasoldt's spring nose-piece for the ordinary Society-screw to carry 

 the objective, and an adjustment for withdrawing at will the cover-glass 

 reflector from the optical axis), consists of an ingenious combination of 

 shutters at the side, by means of which light is admitted only through 

 a long narrow slit that is adjustable in both width and position. With 

 this arrangement a variety of bright- or dark-field effects were obtained 

 by slight changes in the position of the lamp and the adjustment of the 

 slit. When the image of the illuminating flame was formed by the 

 objective just at the edge of the field of view and slightly out of the 

 plane of -the object, a transparent effect was produced over a considerable 

 portion of the field, presumably by internal reflection at the bottom of 

 the dry-mounted cover-glass, on the lower surface of which the lines 

 were ruled, and in the bright portion of the field the lines of the lower- 

 middle bands were very easily and distinctly seen. 



Starting from any of the coarser bands, where there could be no 

 question about the lines, the plate was moved across the field by means 

 of the steady mechanical stage, and the lines of successive bands ap- 

 peared with distinctness, but increasing firmness, up to the band claiming 

 110,000 to the inch, which was seen with perfect ease, and the alleged 

 120,000 which was seen clearly and repeatedly, though with difficulty, 

 while in higher bands no trace or suspicion of lines was perceived. The 

 same limit was reached in several separate trials by the writer, whose 

 eyes, however, by reason of long over-use, should set no limit against 

 the reasonable claims of others presuming to go further. Mr. Fasoldt 

 himself did not seem to recognize the lines nearly as far up in the series 

 as this ; but his son, Ernest C, who was depended upon for most of the 

 manipulation, was positive that he saw the lines in the " 130,000 " band, 

 and none beyond that. Any importance attached to his judgment at 

 this interesting point must be received in connection with the fact that 

 on another occasion he was satisfied that he resolved a " 200,000 " band. 

 No attempt to measure the spacing of the lines was made at that time, 

 and none is ready to report now. 



Mr. Fasoldt's faith in the integrity and visibility of the still higher 

 bands, which faith, it is scarcely necessary to say, is not known to be 



1888. Y 



