100 



THE AMEEICAN MONTHLY 



[May, 1881. 



April 1st, 1881 ; Dr. Carter, President, in 

 the Chair. 



The Hon. Secretary announced the do- 

 nation of twelve microscopic slides from 

 A. C. Cole, Esq., London, Hon. Member, 

 and the Journal of the Quekett Club, 

 from the Club. 



The President then called upon Mr. 

 Mayall, Jr., F.R.M.S., for his communica- 

 tion on " Brass and Glass." 



Mr. Mayall said that it had recently 

 been most ungenerously stated in public 

 that the " Brass and Glass " party, among 

 the microscopists, cared for nothing but 

 mere display of elaborate apparatus ; that 

 they vied with each other in encouraging 

 the manufacture of more and more ex- 

 pensive instruments for the gratification 

 of their personal whims and fancies, and 

 without the slightest reference to advanc- 

 ing any scientific branch of microscopy. 

 It was no part of his programme to ex- 

 plain in detail what really was expected 

 to be gained by encouraging opticians 

 to construct stands, objectives, conden- 

 sers, etc., which, from their elaboration, 

 must necessarily be costly ; but he might 

 point generally to the fact that the most 

 conspicuous developements in recent mi- 

 croscropy — particularly the delineation of 

 microscopic objects by means of micropho- 

 tography — were absolutely dependant on 

 the perfection of the instrument. Now 

 the improvement of the instrument itself 

 was, by no means, so petty a subject 

 as it had been insinuated. He (Mr. 

 Mayall) thought that a thorough investi- 

 gation of the principles upon which the 

 improvement of the instrument depended 

 was, by no means, an unworthy or idle 

 task ; and he thought that if those prin- 

 ciples were more generally appreciated, 

 much more rapid strides would be made, 

 and certainly there would be far less pub- 

 licity given to crude and erroneous inter- 

 pretations ; the ground would, in fact, be 

 cleared of much mere controversial verbi- 

 age. Taking as an example the preval- 

 ence of erroneous views, with regard to 

 the meaning and function of aperture, he 

 would endeavor to present to the meeting a 

 clear statement of the old theory of this mat- 

 ter, and meet it point for point by the newer 

 views, of which Prof. Abbe, of the Uni- 

 versity of Jena, was the originator. Then, 

 by means of a large number of diagrams 

 which he drew on the black-board, illus- 

 trating his subject, Mr. Mayall dealt at 

 considerable length on the main features 

 of what he termed the " aperture con- 

 troversy," concluding his remarks on that 



branch by an earnest appeal to all pres- 

 ent, if they had any difficulties to suggest 

 them forthwith, as it was the ardent de- 

 sire of himself, and those with whom he 

 was associated in the controversy, to have 

 every point of difference thoroughly ex- 

 plained, their sole motive being the pro- 

 mulgation of accurate ideas. Mr. Mayall 

 also exhibited and described in detail sev- 

 eral specimens of " Brass and Glass," 

 some of which he commended to the 

 notice of the meeting, whilst of others he 

 said, " the least said the better." Among 

 the former were Tolles's microscope, with 

 vertical disk for the lateral rotation of the 

 substage, with two stages of novel cons- 

 truction ; Ross's new mechanical stage ; 

 Crouch's "students" microscope, with ap- 

 proximately frictionless fine adjustment ; 

 Parkeschild's portable microscope, etc., 

 etc. In conclusion, a hearty vote of 

 thanks was accorded to Mr. Mayall. 



The meeting terminated with the usual 

 conversazione. 



Exchanges. 



[Exchanges are inserted in this column without 

 charge. They will be strictly limited to mounted 

 objects, and materia] for mounting.] 



Wanted — good gatherings of Diatoms, fossil or re- 

 cent, especially of test forms. Liberal exchange in fine 

 slides ; prepared or rough material. Lists exchanged. 



C. L. PETICOLAS, 635 8th Street, Richmond. Va. 



Section of Brain, stained, showing Tubercular Men- 

 ingites ; also Carcinoma Cerebri. Please send list. 

 L. BREWER HALL, M. D., 27 South i6th Street. 



Good, uncleaned Diatomaceous material containing 

 A rachnoidiscus^ Heliopelta, Pleurosig^iia, IstfnHia, 

 Triceratiitmy Surirella ge77tina and Terpsino<B 

 wMi-zVa wanted, in exchange for well-mounted slides 

 of arranged diatoms, etc., or cash. 



DANIEL G. FORT, Oswego, N. Y. 



Well-mounted Histological and Pathological slides, 

 in exchange for o\h.e.x first-class slides. 



LEWIS M. EASTMAN, M. D., 

 349 Lexington Street, Baltimore, Md. 



Well-mounted diatoms, in exchange for any well- 

 jnounted slides or material, etc. 



W. H. CURTIS, Haverhill, Mass. 



For diatoms in situ on Algse, send mounted slides. 

 K. M. CUNNINGHAM, Box 874, Mobile, Ala. 



For exchange : Mounted thin sections of whale- 

 bone, soapstone, serpentine, albite, feldspar, etc.; 

 also opaque mounts of several very beautiful fossil- 

 iferous limestones. 



Rev. E. A. PERRY, Quincy, Mass. 



Slides of hair of Tarantula, very curious ; also 

 crystalline deposits from urine, to exchange for well- 

 mounted slides. S. E. STILES, M. D., 



log Cumberland St., Brooklyn, N. Y. 



