CORRESPONDENCE. 255 



used. A plate three inches long and one inch wide has a central 

 aperture nearly one-half inch wide, the edges of this opening being 

 bevelled away below so as to admit a large angle of light. Upon this 

 plate lies a glass slip about 2 in. x i in., pressed against at one end 

 by a spring, and at the other end by a screw, so that it can be easily 

 slid backwards and forwards under the two staples (one inch apart) 

 which hold it upon the surface of the plate. The slip is formed by 

 the edges of two slips of platinum foil (-001 thick) one of which is 

 cemented with Canada balsam upon the glass slip, while the other is _ 

 fastened under one of the staples so as to lie on the glass slip but not ' 

 move with it. These platinum slips never overlap ; but their edges 

 may be brought in contact, or may be separated as widely as desired 

 by means of the set-screw pressing against one end of the glass slip 

 which carries one of them. In measuring angles the usual method of 

 rotating the instrument horizontally is employed ; only this apparatus 

 lies upon the stage with its slit in focus of the objective, and adjusted 

 in width so as barely to include the whole breadth of the focus. If 

 the stage of the microscope is too thick to admit full angle of light, 

 the apparatus may be arranged below the stage, and the objective 

 focussed down to it. 



A New Microscopical Society has, we are glad to perceive, been 

 established at Memphis, Tenn., U.S.A. Its bye-laws bear date 

 August 28, 1874, and are terse and to the point. It numbers about 

 twenty-six members, Dr. Cutler being its President, and Mr. S. F. Dod 

 its Secretary and Treasurer. We wish it every success, and hope to 

 have some contributions to our Society from its members. 



The Leeds Public Library.— We have much pleasure in acceding 

 to the Librarian's wishes — making known to those of our readers who 

 may reside in the neighbourhood of Leeds the fact that the Leeds 

 Public Library contains an admirable and considerably large selection 

 of Natiu'al History and Microscopic works. It is a public, and there- 

 fore a free, library, and its catalogues are published in separate 

 sections ; that which we have seen being devoted to natural history, 

 or biology in its widest type. We notice in it some few errata, which 

 we hope to see removed as soon as possible. Who, for instance, is 

 E. Lambert, who is stated to be one of the Editors of the ' Quarterly 

 Journal of Microscopical Science '? 



COERESPONDENCE. 



Beneche's No. 7 Objective. 



To the Editor of the ^Monthly Microscopical Jouryml.' 



Norwich, October 8, 1874. 



Sir, — Having recently obtained one of Beneche's No. 7 objectives 



and submitted it to one or two sharp trials, I am able to confirm Mr. 



Hickie's report of the performance of these glasses. Mr. Hickie says 



the one he tried was equal to a " weak English \." Mine I should call 



VOL. XII. T 



