PHYSICS. 333 



instruments by Oertliing, Bomliu, Alvergniat, Simmon, and the Societe 

 Geuevoise. During tlie year the director has verified the lengths and 

 expansion coefficientsof several standard meters, and Las determined the 

 weights and si^ecifio gravities of several standard kilograms for different 

 governments and scientific authorities. The results of the comparison 

 of the new kilogram prototype with the old kilogram des Archives are 

 given and also a report on the verification at Paris of certain British 

 standards. (iSTature, May, 18SG, xxxiv, 79.) 



Mayer has described a modified form of spherometer, which he calls 

 the well-spherometer, which 'is especially adapted to measure the 

 radii of curvature of lenses of very small linear aperture. The novel 

 feature of the apparatus is the well, a cylindrical aperture into which 

 the screw of the spherometer passes. Placing a piece of flat glass 

 against the lower opening of tlie well {which is for this purpose screwed 

 into a flat plate resting on three feet), a reading of the instrument is 

 made. Replacing the flat glass by the lens to be measured, which ob- 

 viously must not be smaller than the aperture of the well, a second 

 reading is taken. Then, knowing the radius of the well, an easy calcu- 

 lation gives the radius of curvature of the. lens. Several very ingeni- 

 ous modifications of the apparatus are also described in the paper. 

 (Am. J. Sci., July, 1886, III, xxxii, 01.) 



In a memoir to the French Academy, Germain has given the results 

 of very accurate determinations of both the astronomical and the geo- 

 detic co-ordinates at Nice, St. Raphael, Toulon, and Marseilles, made 

 for the purpose of studying the deviation from the vertical produced 

 by the action of topographic relief of the surface. It follows from these 

 four determinations that on the south coast .of France the continent 

 attracts the vertical, that is to say, it repels the astronomical zenith rel- 

 ative to the geodetic zenith. The eflect is the same as if the attraction 

 was exerted by a point situated to the northward of Nice, in the mass 

 of the Alps.— (C. R., May, 188G, cii, 1100.) 



Deprez has suggested the employment of electricity for recording the 

 oscillations of a pendulum. To the pendulum is attached a screen fur- 

 nished with a slit. The light from a petroleum lamp, passing through 

 this slit at each oscillation, falls on a linear thermopile and generates an 

 electric current. This may be used to move the needle of a galvanom- 

 eter, which acts as a relay and brings in an auxiliary current to oper- 

 ate a suitable recording instrument. (0. R., June, 188G, cii, 1523.) 



A paper on the dynamics of bicycling was read before the Dublin 

 University Experimental Science Association by Gerald Stouey. In 

 conjunction with his father, G. Johnstone Stoney, he had made exper- 

 iments to determine the energy necessary to propel a bicycle. They 

 found that when the velocity was 9 miles an hour, it required about 

 5,500 foot pounds per minute, and that it often rose higher than 10,000 

 foot-pounds per minute, the highest the apparatus was capable of re- 

 cording. Their results on the i)ower which a man can exert were higher 



