1884.] 



MICROSCOPICAL JOURNAL. 



233 



the black divisio is in Saturn's rings 

 to the astronomer. This black line 

 is thus caused. Light is stopped at 

 the edge where the transpai'ent mem- 

 brane is folded back. As an illustra- 

 tion — if gold leaf, which is trans- 

 parent and about i -200,000th of an 

 inch thick, be doubled back, at the 

 line of doubling or folding a black 

 line appears in the translucent blue of 

 the leaf. I have seen the same thing 

 on folding carefully a piece of gold- 

 beater's skin. No light shows through 

 at the line of folding. All transparent 

 tubes visible in the best possible in- 

 struments show also too black for 

 borders. In the same way each of 

 the ribs of these scales ^vhen un- 

 clouded with beading or molecules 

 exhibit these beautifully well-defined 

 black lines. Any one who possesses 

 an instrument which clearly and 

 sharply displavs these black margins 

 in minute delicate scales mav be con- 

 gratulated on the superlative excel- 

 lence of his instrument. 



EDITORIAL. 



Publisher's Notices. — All communications, re- 

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The first volume, 1880, is entirely out of print. The 

 succeeding volumes will be sent by the publisher for 

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Vol. II (1881) complete. $1 50. 



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Vol. V (1884) complete, ^1.50. 



Vol. V (1884), Nos. 2-12, $1.00. 



— The subscription-price for the 

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 scribers. 



End of Volume V. — Although 

 five years is but a short span in an 

 average lifetime, they may witness 

 many changes, and bring forth abun- 

 dant fruit in scientific discovery and 

 progress. To us they have been rapid 

 years. Measured by the results of 

 individual industry, they may seem 

 for the most part barren — yet here 

 and there one may find the stepping- 

 stones which bear evidence of pro- 

 gress, and an upward tendency. 



While a retrospective glance over 

 the field of mici^oscopy would be of 

 interest, and while it would show with 

 what rapid strides new ideas have 

 made their way into the minds of stu- 

 dents and observers, and have become, 

 in fact, v^'orking hypotheses with 

 many, we are unable now to give suf- 

 ficient thought to so great a subject. 

 We would only recall to mind the 

 fact, that when this Journal was 

 started the subject of vision with the 

 microscope, as at present understood, 

 had scarcely been outlined in this 

 country. The researches of Prof. 

 Abbe had, indeed, been alluded to 

 here and there ; but no connected or 

 intelligible account of them had been 

 published. The true functions of an- 

 gular aperture were not known, 

 and homogeneous-immersion objec- 

 tives were scarcely heai'd of. Not 

 that the subject was not at that time 

 understood, for Prof. Abbe's elabo- 

 rate paper had been published several 

 years before, and a translation had 

 also appeared in England, which, 

 however, was but little known. 



There was needed a journal which 

 would keep its readers informed not 

 only concerning the work that was in 

 progress in this country, but also in 

 England, Germany, and France. At 

 an opportune moment this Journal 

 was established and received cordial 

 support. It has endeavored to fill a 



