400 SCIENTIFIC RECORD FOR 1882. 



final result being a loss of 22.3 seconds, agreeing •with that given by 

 Adams. {J. Fhys., February, 1882, II, i, p. 61.) 



Sherman has studied the effect of the support on the oscillations of a 

 pendulum. The decrement of the arc could not be represented by a 

 smooth curve, and, on examination, it was found to be due to small 

 movements of the stand not synchronous with those of the pendulum. 

 This resulted in one case from the nature of the ground on which the 

 stand rested, in another from the varying tightness of the joints of the 

 stand due to the dryness of the w^ood, and in a third from the vibration 

 of a clock on the same wall. {Am. J. Sci., September, 1882, III, xxiv, 

 p. 175.) 



Jolly has applied the balance to the determination of the mean density 

 of the earth. To each arm of the balance a rod 21.5 meters long was 

 attached, carrying pans at the upper and lower ends. The weights were 

 balls of glass filled with mercury and weighing 5 kilograms. Two of 

 these weights were j)laced in the upi)er pans, and equilibrium obtained 

 by adding weights, the displacement being observed by means of a 

 mirror, scale, and telescope. One of the weights being transferred 

 to the lower i^an, its weight was found to be increased by 31.713 

 milligrams. Introducing, now, a sphere of lead 0.995 meter in diameter 

 and weighing 5,775.2 kilograms, beneath the lower pan, the increase of 

 weight was found to be 32.059 milligrams, a mfean difference in a series 

 of experiments of 0.589 milligram. From this the mean density of the 

 earth is calculated as 5.692, a number higher than that usually given, 

 but correct probably for the locality (Munich). {J. Phys., May, 1882, 

 II, I, p. 231.) 



Wolf has carefully examined and identified the various standards of 

 weight and measure which are deposited in the Observatory of Paris. 

 These are: 1st, the standards known as"latoisedu Perou," and "la 

 toise du Nord," both in excellent condition; 2d, the four compound 

 rules of copper and platinum used for measuring bases, the pendulum 

 rule of Borda and Cassini, a meter and double meter in iron, and one 

 of the four original standard meters of platinum, the others being the 

 meters of the Archives, of the Conservatoire, and of the Commission des 

 Pouts et Chaussdes, respecti.vely ; 3d, two of the four original platinum 

 kilograms, the others being the kilogram of the Archives, and the kilo- 

 gram of the Conservatoire ; and 4th, the fourrmeter copper rule of Lenoir 

 used by Lavoisier, Borda, and the Commission of 1798 in comparing the 

 toises and standardizing the'meter. [J. Phys., June, 1882, II, i, p. 252 ; 

 Ann. Chim. Phys., January, 1882, V, xxv, p. 5. 



Wead has suggested a simple mode of changing the gear of an ordi- 

 nary screw-cutting lathe so as to allow threads of one millimeter pitch 

 to be cut by it. It is based on the assumption that one inch equals 25.4 

 millimeters; which differs from the fact by only yi o\ o o part. The lathe 

 is first geared so as to cut a screw of 20 threads to the inch, a gear of 

 100 teeth being on the feed-screw. Then this gear of 100 teeth is re- 



