OF ARTS AND SCIENCES. 73 



Four hundred and eiglity-eigltth meeting* 



November 14, 1860. — Statute Meeting. 



The President in the chair. 



The Corresponding Secretary read letters received since the 

 preceding meeting. 



Mr. E. B. Elliott read a paper " On the Calculus of Affected 

 Quantities," in which was proposed a general unit-symbol of 

 mononomial form, intended to embrace as particular cases, 

 and to define the several aifective symbols of, single, double, 

 and quadruple algebra. 



Professor J. Wyman presented and gave an analysis of a 

 paper by Dr. John Dean, on the minute structure of the 

 spinal cord. 



Professor "William B. Rogers described a simple application 

 of the camera lucida for obtaining twin drawings, suitable for 

 combination in the stereoscope. 



For this purpose the reflecting prism, movable along a horizontal 

 rod, must be adjusted successively in the positions proper to the right 

 and left eyes respectively, when these are directed upon the object. 

 The two pictures projected on the horizontal paper below, and traced 

 out in the usual way, will represent the two aspects of the object as 

 seen by the I'ight and by the left eye severally, and, when united by 

 means of binocular combination, they will reproduce the object visually 

 in all its original relief. 



As connected with the same subject. Professor Rogers re- 

 ferred to an arrangement for the binocular analysis of a per- 

 spective physical line described by him some years ago in the 

 American Journal of Science. 



In this the line was placed directly behind a vertical plate of clear 

 glass, while the observer, keeping his head in a fixed position, viewed 

 the line with one eye at a time, tracing on the glass the projections 

 corresponding to its appearance, as seen by the right and left eyes 

 respectively. The projections thus drawn will, of course, when binocu- 

 larly combined, reproduce the original perspective line. In the same 

 manner, a more complex object placed behind the glass plate may be 

 represented m its two projections by pictui-es capable of a perfect 

 binocular combination. 



VOL. V. 10 



