80 abstracts: terrestrial magnetism 



TERRESTRIAL MAGNETISM.— Results of magnetic observations made 

 by the Coast and Geodetic Survey between July 1, 1909, and June SO, 

 1910. R. L. Faris. App. No. 3, Rept. for 1910, pp. 71-141. 1911. 



This publication contains the results of magnetic observations made 

 on land and at sea by the Coast and Geodetic Survey in the prosecution 

 of the magnetic survey of the United States and outlying territories 

 during the fiscal year ended June 30, 1910, including the determinations 

 of the magnetic elements in 39 States and Territories. The results on 

 land are tabulated by States and in the order of increasing latitudes of 

 the stations. During the year observations were made at seventy-five 

 (75) old stations to ascertain the secular change of the magnetic elements. 

 Results of observations on the Atlantic and Pacific oceans and in the 

 Philippines are grouped in separate tables. The latter portion of the 

 report is devoted to the descriptions of land stations, including their 

 permanent markings and true bearings from them to permanent objects, 

 which are of use to local surveyors, especially where true meridian lines 

 were established in conjunction with the magnetic work. R. L. F. 



ELECTRICITY. — The electrical conductivity of commercial copper. 

 F. A. Wolff and J. H. Dellinger. Bulletin Bureau of Standards, 

 7: 103-126. 1911. 



A reliable average value for the conductivity of the copper furnished 

 for electrical uses was desired by the American Institute of Electrical 

 Engineers, to be used as the basis of new tables, to replace their old 

 Copper Wire Table of 1893. The Bureau of Standards was asked to 

 obtain the data, and copper samples from representative sources were 

 investigated. Besides the samples measured extensive data were 

 obtained from a large manufacturing company. The mean of the data, 

 representing tests on more than 100,000,000 pounds of copper, was 

 practically the same as the value previously assumed for the resistivity 

 of annealed copper, in the preparation of wire tables and in the expres- 

 sion of per cent conductivity, etc., viz., 0.153022 ohm per meter-gram at 

 20° C. This value is to be called the "Annealed Copper Standard." 



The conductivity of hard-drawn wire of about 2 mm. diameter was 

 found to be less than the conductivity of annealed wires by a mean value 

 of 2.7 per cent. The difference between the conductivity of annealed 

 and hard-drawn wires increases as the diameter decreases. The highest 

 conductivity found was that of a wire drawn directly from a mass of 

 native lake copper, viz., 101.71 per cent of the conductivity of the 



