xxxvi GENERAL SUMMARY OF SCIENTIFIC AND 



The brilliant experiments of Le Roiix on peripolar induc- 

 tion, as well as the new magneto-electric machine of Gramme, 

 have prepared the way for an exact determination of the co- 

 efficient of equivalency of ibrce and electricity. Tlie effect 

 of galvanic currents on the dimensions and elasticity of me- 

 taliic conductors has been studied by Streiutz and Mayer 

 respectively. The observations by Villari on the time re- 

 quired to magnetize and demagnetize glass gives us a new 

 relation between the electric and molecular forces. 



During the year there have passed away Sir Francis Ro- 

 nalds and August de la Rive, names equally honored in their 

 respective countries. 



The older theories of the nature of molecules and molecu- 

 lar actions seem at present to be giving way before the sur- 

 prising success of the advocates of the dynamical theory of 

 the constitution of gases, the principles of which theory have 

 been established by Stephan, Clausius, Meyer, Maxwell, and 

 others, upon an exceedingly firm basis. The recent address 

 of Maxwell on molecules gives the most recent results of the 

 studies of these investigators. 



PHYSICS. 



In the allied departments of OjMcs and Acoustics the ac- 

 tivity has been very considerable, and we can here only 

 mention those items that have a comparatively imjoortant 

 and permanent bearing upon the progress of science : such 

 are Weinhold's investiixations into the measurements of hio-h 

 temperatures; J. W. Draper's Essays upon the actinic, optic, 

 and thermic powers of different portions of the spectrum ; 

 and Henry Draper's photographs and measurements of the 

 diffraction spectrum. 



One of the most remarkable discoveries, interesting alike 

 to the practical photographer and the physicist, is announced 

 in a short dispatch from Dr. Yogel, of Berlin. This consists 

 in the invention of chemical compounds, that may at will be 

 made sensitive to the rays of greatest or least refrangibility. 



Lord Raylcigh has submitted a short but important and 

 suggestive memoir on the reflection of sound waves from a 

 fiurliice composed of numerous regularly arranged smaller sur- 

 faces. 



Professor Mayer, of the Stevens Institute of Technology, 



