192 



SCIENCE. 



[N. S. Vol. V. No. 109. 



ponent {X) of the earth's magnetic force, and 

 to their secular variations, A Fand /\ X. After 

 obtaining the mean value of F, for example, 

 for a given parallel of latitude, he subtracts 

 this from the values at selected points on that 

 parallel. After proceeding thus for various 

 latitudes he joins the places by lines where the 

 residual F has the same value, these lines being 

 his 'isanomolous lines.' He finds that the X 

 isanomolous lines present the same general 

 characteristics as those of H (horizontal compo- 

 nent), the F as those of D (declination), and 

 the Z (vertical force) as those of I (inclination). 

 The same applies with regard to the secular 

 variation of the components and elements. 

 There is, furthermore, a strong resemblance 

 between the respective isanomolous lines and 

 lines of equal secular variation. 



On the Distribution and the Secular Variation 

 of Terrestrial Magnetism. No. IV. : On the 

 Component Fields of the Earth's Magnetism. 

 By L. A. Bauer. This paper is a continuation 

 of the author's researches to localize the cen- 

 ters of disturbance in the earth's permanent 

 magnetic field. He resolves the total field into 

 three components, as follows : 



I. A homogeneous magnetization about the 

 rotation axis. 



II. A homogeneous magnetization about an 

 equatorial diameter. 



III. The residual magnetization, i. e., that 

 which remains after deducting I. and II. 



A striking graphical representation of No. III. 

 is given. It is found, among other things, that 

 the residual field and Schuster's diurnal varia- 

 tion field exhibit a strong resemblance. 



Dr. Borgen, of Wilhelmshaven, contributes a 

 valuable article in which he develops the most 

 general expression for the coefficients in the 

 formula giving the angular deflection of a mag- 

 netic needle produced by a deflecting magnet 

 arbitrarily placed. After discussing the general 

 case he takes up special cases ordinarily met 

 with in practice. 



Mr. Baracchi, the director of the Melbourne 

 Observatory, gives an interesting account of 

 'Magnetic Work in Australia.' It seems un- 

 fortunate that no means have been found thus 

 far to reduce and discuss the observations ex- 

 tending over thirty years. 



Next follow editorial notes, reviews by Schott, 

 Littlehales, Solander and P. W., and a list of 

 current publications. This number concludes 

 volume I. 



SOCIETIES AND ACADEMIES. 



THE SCIENTIFIC ASSOCIATION OF THE JOHNS 

 HOPKINS UNIVERSITY. 



The one hundred and twenty-ninth regular 

 meeting, President Remsen in the chair. The 

 following papers were presented and read : 



' Recent Researches on Metallic Carbides and 

 Allied Compounds,' by Edward Kenouf. 



The recent application of the electric arc as 

 a means of obtaining very high temperatures 

 has stimulated research on metallic compounds 

 formed at high heat and unstable in contact 

 with water, hence not found in nature. We owe 

 knowledge of the carbides or compounds of 

 metals with carbon, principally to Moissan. 

 Most metallic carbides are made by heating ox- 

 ides with carbon at temperatures varying from 

 3500° to 5000°. They are metallic substitution 

 products of hydrocarbons, and as a rule yield 

 hydrocarbon and metallic hydroxide in contact 

 with water. Some are acetylides yielding pure 

 acetylene, as is the well-known calcium carbide 

 used for the technical preparation of acetylene. 

 Aluminium and beryllium carbides are methides 

 yielding pure methane. Many other carbides, 

 notably those of uranium and iron yield com- 

 plex mixtures of saturated and unsaturated, 

 gaseous liquid and solid hydrocarbons. Moissan 

 thinks that natural gas and petroleum are formed 

 by action of water on carbides contained in the 

 earth's crust. Considering the evidence, this is 

 the most acceptable solution of the problem of 

 the formation of petroleum and natural gas yet 

 oflFered. Metallic nitrides, compounds of metals 

 with nitrogen, are mostly made by contact of 

 nitrogen with metals at high temperatures ; 

 some by the action of ammonia on metals at 

 high temperatures, when hydrogen escapes and 

 the metallic nitrides are formed. They are de- 

 composed by water into ammonia and metallic 

 hydroxides, hence must be regarded as substi- 

 tuted ammonias. 



Metallic silicides, compounds of metals with 

 silicon, are formed by heating metals with sili- 



