September 24, 1909] 



SCIENCE 



413 



Lehrbuch der Kristalloptik, by E. B. Wilson; 

 " Notes " ; " New Publications." 



SPECIAL ARTICLES 

 ON MAGNETIZATION BY ANGULAR ACCELERATION 



Some time ago, while thinking about the 

 origin of the earth's magnetism, it occurred to 

 me that any magnetic substance must, accord- 

 ing to current theory, become magnetized by 

 receiving an angular velocity. 



Thus consider a cylinder of iron or other 

 substance constituted of atomic or molecular 

 systems whose individual magnetic moments 

 are not zero. The simplest ideal system of 

 this kind is of course a negative (or positive) 

 electron revolving about a positive (or nega- 

 tive) center. In its initial state the magnetic 

 moment of the cylinder composed of all the 

 systems is zero. If, however, it is given an 

 angular acceleration about its axis, the result- 

 ing torque on each individual system will 

 cause its orbit to change its orientation, or 

 the revolving part its speed, in such a way 

 as to contribute a minute magnetic moment 

 parallel to the axis of the cylinder, all 

 the systems, if alike, contributing moments in 

 the same direction. If the revolving electrons 

 are negative, as appears at least generally 

 to be the case, the cylinder will become mag- 

 netized as it would be by an electric current 

 flowing around it in a direction opposite to 

 that of the angular velocity imparted to it. 

 Early in July I began some experiments on 

 this subject, using slightly modified apparatus 

 constructed originally for other purposes. 

 These experiments appear to show the effect in 

 question in the case of a large steel rod, the 

 intensity of magnetization resulting when an 

 angular speed of about 90 revolutions per sec- 

 ond was produced being about ^r,oo c.g.s. 

 unit, in the direction indicated by theory on 

 the assumption that the revolving electrons 

 are negative. This effect, if substantiated by 

 later work, will account for a minute part of 

 the earth's magnetism, but, apparently, for 

 only a minute part. It is the converse of the 

 effect which has been looked for recently by 

 Richardson. 



Superposed on this effect was another, per- 



fectly definite and unquestionable, but exceed- 

 ingly difficult to account for, viz., a magnetiza- 

 tion along the rod in a definite direction inde- 

 pendent of the direction of rotation and of the 

 direction of the original residual magnetism 

 of the rod. It was not due to the jarring of 

 the cylinder as it was rotated in the earth's 

 field, nor to a possible minute change in the 

 direction of its axis produced by the pull of 

 the motor. In magnitude this effect was sev- 

 eral times as great as the other, which became 

 manifest only at the higher of the two speeds 

 used. 



The observations were made inductively 

 with a ballistic galvanometer. The throws 

 were very small, but definite, and were in op- 

 posite directions for starting and stopping. 



Later on I hope to investigate this subject 

 more thoroughly with apparatus designed for 

 the purpose. I am sending this account to 

 you because of the importance of one of the 

 effects mentioned, and the fact that some 

 months must elapse before a thorough investi- 

 gation can be undertaken. 



S. J. Barnett 



August 5, 1909 



NITRIFYING BACTERIA IN NORTH CAROLINA SOILS 



In a recent number of Science' Stevens and 

 Withers present some interesting data con- 

 cerning the existence in North Carolina of 

 non-nitrifying soils. It was pointed out that 

 71 per cent, of 62 soil samples representing, 

 with few exceptions, normal agricultural soils 

 near the North Carolina Agricultural Experi- 

 ment Station failed to nitrify, a state of affairs 

 considered anomalous. 



At the time of the publication of this paper 

 the Laboratory of Soil Bacteriology of the 

 Bureau of Plant Industry was receiving a 

 number of soil samples from fields or plots 

 where legume inoculation experiments were in 

 progress. Thirty samples from crimson clover 

 fields in North Carolina (representing nine- 

 teen counties) were submitted to a test for 

 nitrification. Seven samples were from the 

 Piedmont Plateau and twenty-three from the 

 coastal-plain region. 



' Science, N. S., XXIX., No. 743, p. .506. 



