816 



SCIENCE. 



[N. S. Vol. II. No. 50. 



tei- evidently betrays an appreciation of Lin- 

 naeus' character and ability and his words indi- 

 cate that he had some expectations as to the 

 future career of his pupil. 



The further treatment of the later life and 

 work of the great naturalist will be awaited with 

 interest. The author remarks that no biogi-aphy 

 of Linnaeus can do him justice, unless it be 

 written on the basis of a thorough knowledge 

 of all the sciences to the development of which 

 he gave his attention. It is only by comparison 

 of these sciences, in the condition in which 

 they were before his time and in the state to 

 which they were brought by his efforts as an 

 investigator and by the powerful impetus of his 

 teaching, that we can truly appreciate the 

 greatness of his work and see its influences ex- 

 tending into our own time. In this age of 

 specialization there is perhaps no one man who 

 has such a wide knowledge of these branches 

 as would be required; and a full account of 

 Linnaeus as a man of science would require the 

 cooperation of several men interested in the 

 difierent departments of natural history. 



J. A. Udden. 



AuGUSTANA College, Eock Island, III. 



SCIENTIFIC JOURNALS. 



PHYSICAL REVIEW, VOL. Ill, NO. 3, NOVEMBER- 

 DECEMBEE, '95. 



Variation in Electrical Conductivity of Metallic 

 Wires in Different Dielectrics. By Fernando 

 Sanford. 



In a paper published in 1892 Prof Sanford 

 presented the results of observations on the re- 

 sistance of copper wires when immersed in diflfer- 

 ent dielectrics, and reached the conclusion that 

 the conductivity was to some extent dependent 

 upon the nature of the dielectric, quite apart 

 from incidental temperature changes, leakage, 

 etc. The change observed in the resistance 

 was small, amounting to not more than 0.2^. 

 Since that time similar measurements have been 

 undertaken by at least one other observer in 

 the hope of verifying Prof. Sanford' s conclu- 

 sions, but without success. The original papers 

 have in fact been quite generally and severely 

 criticised. 



In the present paper Prof. Sanford discusses 

 the sources of error which have been suggested 

 as accounting for his results, and calls attention, 

 to the fact that his conclusions have recently 

 been qualitatively verified by Grimaldi and 

 Catania with more accurate apparatus than he 

 had himself used. The paper also contains the 

 results of further observations on copper and 

 silver wires. The amount of the resistance 

 change was found to differ greatly with different 

 samples of wire ; but the direction of the change 

 was always the same for a given material. 

 Thus the resistance of copper was less in petro- 

 leum than in air, while with silver the resistance 

 was found to be less in air. Strangely enough the 

 behavior of a silver wire which had been copper- 

 plated was almost identical with that of pure 

 silver. The results obtained are certainly diffi- 

 cult of explanation, but are the more interesting^ 

 on that account. 



A Study of the Polarization of the Light Emitted 



by Incandescent Solid and Liquid Surfaces. II. 



By R. A. MiLLiKAN. 



The first half of this paper, dealing with the 

 qualitative study of polarization by emission, 

 has already been noticed in Science. In the 

 present article the subject is treated quantita- 

 tively. The substances investigated were plati- 

 num, silver, gold and iron, the first two men- 

 tioned proving most satisfactory. 



By means of a simple but accurate polarimeter 

 the amount of polarization was measured at 

 different angles of emergence. The results- 

 were then compared ^ith the values given by 

 Cauchy's theory of metallic reflection, upon the 

 assumption that the polarization is due to the 

 refraction of the rays from the interior on emerg- 

 ing from the surface. The agreement between 

 the computed and observed values is quite 

 striking, and makes it appear that refraction at 

 emergence offers a satisfactory explanation of 

 the phenomena in all the cases investigated. 

 The agreement is especially good in the case of 

 molten silver. 



Observations upon the light developed by 

 fluorescence at the surface of Uranium glass 

 show that the light is polarized much in the same 

 way as the rays from an incandesceut surface. 

 Here, too, the effect may be explained as a result 



