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Societies and Academies

    Naturevolume 43pages4748 (1890) | Download Citation




    Royal Microscopical Society, October 15.—Dr. C. T. Hudson, F.R.S., President, in the chair.—Mr. G. F. Dowdes-well's note on a simple form of warm stage was read, and the apparatus exhibited.—The President said he had with great regret to record the deaths of two honorary Fellows of the Society—Prof. W. Kitchen Parker, F.R.S., and Mr. J. Ralfs. In place of these two gentlemen Dr. H. B. Brady, F.R. S., and Prof. W. C. Williamson, F.R.S., were nominated.—Mr. Mayall said he must ask the indulgence of the meeting to enable him to clear himself from possible ambiguity. In notifying the fact that at the first photographic trials of the new objective of 1˙6 N.A. the visual and actinic foci had been found by Mr. Nelson and himself to be not coincident; and that when the objective was returned to Jena immediately after, Dr. Czapski found the foci were coincident; he had hazarded what he had imagined would appear a mere playful admission of the state of general puzzlement of both sides by suggesting that “the transit of the objective from London to Jena had somehow got rid of the ’chemical’ focus.” That sentence had unhappily been construed both in England and abroad into a reflection upon the good faith of Dr. Czapski, or Dr. Abbe, or the firm of Zeiss. Whatever blame was due to himself for the ambiguity of the expression, he must, of course, accept. At the same time he thought the Society would be interested to learn that upon his conveying his explanation to Dr. Czapski and Dr. Abbe, those gentlemen had expressed their complete satisfaction with it. He believed that the existence of a “chemical” focus was probably due to a slight difference in the adjustment of the front lens, especially, as Dr. Abbe had pointed out, in view of the fact that with an objective of such large aperture the colour correction was, as it were, “balanced on a needle-point” in the matter of an alteration in the distance of the front lens from the posterior combinations; and that a very minute alteration in that distance, though producing no perceptible difference in the visual image, was quite competent to lengthen or shorten the focus of the violet rays to such an extent as to exhibit a “chemical” focus non-coincident with the visual focus when tested photographically. —The President gave formal notice that a special general meeting would be held in the Library at 5 p.m. on Wednesday,. October 22, for the purpose of considering alterations in the bye-laws, the terms of which he read.—Mr. G. C. Karop exhibited and described an improved students' microscope, made by Swift and Son. The new instrument embodied Mr. Nelson's “horseshoe” stage for convenience of readily seeing the condenser, and for estimating by the touch the approximation of the focus on the slide, and on which the Mayall mechanical stage was easily applied, together with a centring sub-stage focussed by sliding on the tail-piece, the whole of superior workmanship and design, and supplied at a moderate outlay.—Prof. J. W. Groves communicated a note by Mr. P. C. Waite on a new method of demonstrating intercellular protoplasmic continuity. A specimen in illustration was exhibited.—Mr. J. D. Aldous exhibited some early forms of microscope slides made of boxwood, similar to those formerly made of ivory, with the objects between pieces of talc.—The President called attention to some original drawings of a new Rotifer by Mr. W. B. Poole, of South Australia; also to a specimen of Æcistes mucicola exhibited by Mr. G. Western.—Mr. E. M. Nelson exhibited upon the screen a series of thirty-one photomicrographs, which he described.—Dr. H. B. Brady's paper on a new type of Foraminifera was taken as read. —Dr. Maddox's paper on the structure of Spermatozoa was postponed until the next meeting in consequence of the lateness of the hour.

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