154 Intelligence and Miscellaneous Articles. 



of glass augments under the action of a mechanical traction ; 

 (2) crystals possessing non-superposable hemihedry of form change 

 their form when submitted to electric forces, and this deformation 

 may sometimes be in an opposite sense to that which electric attrac- 

 tion would itself produce ; (3) a pyroelectric crystal is warmed or 

 cooled by the approach of an electrified body, according to whether 

 the body be positively or negatively electrified. 



The phenomena thus foreseen are the inverse of the phenomena 

 from which they are respectively deduced. To establish their ex- 

 istence, equation (a) is in each case necessary. Finally, we may 

 remark that the sense of the inverse phenomenon may always be 

 defined by the following rule, which is an extension of that given by 

 Lenz for induction : — The inverse phenomenon is always of such a 

 sense that it tends to oppose the production of the primitive phenomenon. 



The process of calculation which I have employed in this memoir, 

 and which consists in translating a physical law by a condition of 

 integrability, was introduced into science by Sir W. Thomson and 

 by M. Kirchhoff. An examination of the work of those eminent 

 physicists will, I think, be convincing that the principle of the Con- 

 servation of Electricity is for Electricity that which the principle of 

 Carnot is for Heat. 



MR, R. SHIDA ON DR. C. R. ALDER WRIGHT S NOTE PUBLISHED IN 

 THE PHILOSOPHICAL MAGAZINE FOR JULY 1881*. 

 In answer to Dr. C. R. A. "Wright's note (page 76, Phil. Mag. 

 for July 1881) on my paper and my recent note, I have to state, 

 (1) that by what I said in my note was meant that the calculation 

 confirmed the truth, in the case of my experiment described in my 

 paper, of the very fundamental law of Ohm, namely 



C= = , or E==.(v— v) — L- 



o-\-r r r 



(an equation identical with that shown in his note after elaborate 

 steps of reasoning), where E denotes the E.M.E. of the cell in 

 the circuit consisting of (b) the internal resistance of the cell and 

 (r) the resistance external to it, and v—v' denotes the difference of 

 potential between the poles of the cell when the current C is flowing 

 through the circuit ; and (2) that what I measured both electro- 

 statically and electromagnetically in my experiment was one and the 

 sameE.M.F., the E of the Thomson gravity Daniell, but not {v—v) 

 the difference of potential between the poles, which I do not call 

 the E.M.E. of the cell as he (Dr. Wright) does. 



[The " two-per-cent." error alleged by Dr. "Wright is a creature 

 of his own imagination, due seemingly to misunderstanding of 

 Ohm's Law \—W. T.] 



* Communicated by Sir William Thomson. 



