334 PHYSICS. 



turned into a true cylinder 40 millimeters in diameter, and cut into three 

 equal parts. The rest of the bar was again drawn down under the ham- 

 mer till it was 25.5 millimeters on a side and 103 centimeters long, an 

 operation lasting 14 hours. It was now put on a planing-machine 

 and planed into the form of an X iu section, this labor requiring 28 

 days, from six in the morning to 10 at night. The bar, which before 

 planing had a weight of 15,500 grams, weighed only 3,584 grams after- 

 ward. On examining the three specimens cut from the ingot, their 

 specific gravities were found to be 21.530, 21.536, 21.538, at 19°, or 21.535 

 as a mean ; that of the pieces cut from the ends of the two rectangular 

 rules being 21.523. The turned cylinders were then submitted, in steel 

 molds, to blows of a hammer, each blow equivalent to a pressure of- 

 110,000 kilograms. The first cylinder received 10 blows, and had a den ; 

 sity of 21.554 ; the second received 20 blows, and its density was 21.5528; 

 the third received 30, and was 21.5531 ; the mean of the three being 

 21.553, with a probable error of ± 0.002. The chips removed by the 

 planer were 21.538 before and 21.548 after melting. On analysis, after 

 purification, the chips from the planer gave Devjlle: iridium, 10.1500; 

 iron, 0.035; ruthenium, 0.017; rhoduim, 0.038; platinum, 89.75. The turn- 

 ings gave: iridium, 10.151; iron, 0.032. In 100 parts of the alloy there 

 were then 10.1444 parts of iridium, or l,018of iridium to9,000of platinum ; 

 a value considerably within the tolerance allowed to Matthey . Collateral 

 experiments showed the impracticability of drawing the bar through a 

 templet of steel, since t-he quantity of iron in the alloy was thus trebled. 

 Finally, the possibility of making separate masses of this alloy uniform 

 in composition and density' was satisfactorily established, the iridium 

 in a third specimen difiering from that in the second and first by only 

 0.0003. The bar now goes to MM. Bruner, for the purpose of having 

 the meter lines transferred to it from the standard meter of the govern- 

 ment. {Ann. Chim. Phys., January, 1881, Y, xxii, 120.) 



Sire has described an apparatus, which he calls a devioscope, for 

 ascertaining directly the relation which exists between the angular ac- 

 locity of the earth and that of a horizon around the vertical of any i^lace 

 whatever. In the well-known pendulum experiment of Foucault, the 

 apparent rotation of the plane of oscillation of the pendulum is propor- 

 tional to the sine of the latitude of the place of observation, in con- 

 sequence of the tendency of this plane to remain always parallel to 

 itself. The apparatus in question consists of a^ fixed globe suppoi'ted 

 on a vertical steel axis carried on an iron tripod. From this support 

 just below the sphere a semicircular arm, articulated in the center, rises 

 to carry a system of three wheels, the diameter of each being exactly 

 the same as that of the sphere. Two of these wheels are toothed and 

 work into each other. One of them moves on an axis i:)arallel, when 

 the semicircle is in its normal position, to the axis of the sphere. The 

 upper part of this axis carries a model of the plane of oscillation. The 

 second wheel is fastened to an axle sup])orted on an arm always at right 



