130 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



THE MOLECULES OF ETHEK. 



In connection with the very interesting lecture of Maxwell 

 on molecules, it is worth while to record the confirmation 

 of his results, recently attained by Herwig. This author, 

 starting from the comparison of the expression for the ther- 

 mal effect of a galvanic current, with the expression for the 

 vis viva represented therein, at any moment, by the motion 

 of the electric particles, and holding fast to the notion of 

 only one electric fluid, obtains, by a series of reasonably ap- 

 proximate assumptions, the conclusion that the weight of a 

 molecule of ether amounts to considerably more than the 

 one-hundredth power of one tenth of a milligramme. 7 A, 

 XLVII.,191. 



TERQUEM'S TONOMETER. 



In order to determine the absolute number of vibrations of 

 any body, Terquem has transformed the vibrascope of Lissa- 

 jous into a tonometer. He had made four diapasons, furnished 

 with cursors, each carrying at the extremity of one of its 

 branches, like the diapason of the vibrascope, a small bicon- 

 vex lens to serve as an objective. The standard diapason was 

 then so fixed that the vibration of any tube or string to be 

 examined could be seen through the convex lens. When the 

 standard and experimental tube vibrated together, and when 

 they vibrated in opposite directions, a phenomenon was per- 

 ceived similar to that of the beats heard when two sounds 

 interfere with each other. By the observation of these beats, 

 it was a very simple matter to decide how frequently the ex- 

 perimental body was vibrating, and thus to determine the 

 tone that issued from it. 



MATHEMATICAL LAWS OF ELASTICITY. 



Professor Curioni, of the engineering school at Turin, has 

 published a memoir upon the law of the molecular resistances 

 in any elastic solid whatever, elicited by any system of forces, 

 and has applied his mathematical deductions to the case of 

 beams compressed, distended, bent, and twisted in various 

 ways. This problem, which has been treated by so many 

 eminent mathematicians since the days of Euler, and which 

 still, in all its generality, eludes the power of the best math- 



