PROCEEDINGS OF SOCIETIES, 295 



Donations to the Library and Cabinet since Oct. 7, 1874 : — 



Nature. Weekly Yvom The Editor. 



Atlieua3iim. Weekly „ Ditto. 



Society of Arts Journal. Weekly „ Society. 



Journal of the Linnean Society. No. 77 „ Ditto. 



Journal of the Quekett Club. No. 27 „ Club. 



Bulletin de la Socie'te Botanique de France „ Society. 



Marvels of Pond Life. By H. J. Slack. 2nd Edition .. „ Author. 



The Protoiihismic Theory of Life. By John Drysdale, M.D. „ Ditto. 



Mechanical Finger „ W.T. Suffolk, Esq. 



Four Slides of Diatoms „ F. Kitton, Esq. 



The following gentlemen were elected Fellows of the Society : — 

 John Eailton Williams, Esq. ; James Wallinger Goodinge, Esq. 



Walter W. EeevES, Assist.-Secntary. 



Medical Microscopical Society. 



October 16, 1874. — Jabez Hogg, Esq., President, in the chair. 



At the first meeting of this Society, for the session 1874-5, a 

 paper communicated by John Gorham, Esq., of Tunbridge, " On a New 

 and Expeditious Method of Micrometry," was read by the President. 



The principle of the instrument described, depended upon the 

 measurement of lines drawn parallel to the base of an isosceles 

 triangle — the bass of the latter being given — by means of the sides, 

 which are divided into a known number of parts. The triangle is 

 obtained by dividing through the centre a disk of brass, about 1^ inch 

 in diameter and half an inch thick, and bevelled at the edge, so as to 

 allow of its being embraced by a stout india-rubber ring, by which 

 means the two portions are held in perfect apposition at the edges 

 of the section. The line of section, for the distance of 1 inch from 

 the circumference, is marked out into fractions of an inch — at least, 

 into 32 parts — a less number being insufficient to obtain accurate 

 results. A piece of paper of known thickness is now inserted between 

 the halves of the disk, and moved along till its edge touches the 

 commencement of the marked inch, the elastic band retaining it in its 

 place, and thus an isosceles triangle, or gap, is left, with a base the 

 thickness of the slip of paper, and with an edge of 1 inch, divided, as 

 stated, into 32 equal parts. If a hair or cobweb be passed along the 

 slit from base to apex, it will be arrested somewhere, and by reading 

 off the number opposite which it stops, a simi)le matter of multiplica- 

 tion, the base of the triangle being known, will give the diameter 

 required. For microscopic purposes the instrument is jilaced on the 

 stage, and the object to be measured, placed on a thin glass cover, is 

 slid over the aj)erture till it exactly at one point spans it. The 

 diameter is then read off. To obtain still greater accuracy, Mr. 

 Browning has added a screw of known value, to separate the halves of 

 the micrometer in lieu of the slip of paper. 



In answer to some questions by members of the Society, the Presi- 

 dent replied that the instrument was specially designed for unmounted 

 objects, the thickness of an ordinary glass slide being rather an objec- 

 tion in the case of mounted ones. A thin glass cover might be in all 

 cases employed for placing the specimen, e. g. blood, or pus, upon. 



