476 



SCIENCE. 



[N. S. Vol. I. No. 17. 



masses. It is simple but effective, and so 

 delicate in its indications that the utmost 

 care was necessary to avoid interference for 

 external causes, often difficult to control. 

 Full details are given, as they are of great 

 interest, especially to those who contem- 

 plate the use of a quartz torsion fibre. It 

 is interesting to note that the author was 

 never able, throughout a long series of ex- 

 periments, to control absolutely the zero 

 point of his balance. Although quartz is 

 enormously superior to any other suspen- 

 sion thus far proposed, it is still defective 

 in this respect. For some cause which Dr. 

 Mackenzie is unable to give, the zero was 

 constantly shifting. He does not clearly 

 say whether this partakes of the nature of 

 a ' drift ' in one direction or not. In a long 

 series of experiments, made by direction of 

 the writer of this notice, for the purpose of 

 trying to improve the existing form of the 

 vertical force magnetometer, quartz fibres 

 were used. Although apparently well pro- 

 tected from convection currents and changes 

 in temperature, the mirror attached to them 

 was never actually at rest. When this shift- 

 ing and drifting is small, as it usually is, 

 and observations are of the nature of those 

 described by Dr. Mackenzie, that is, not in 

 themselves extending over long periods, the 

 error arising from it may be readily and 

 correctly eliminated. 



The apparatus used for observing the at- 

 traction of isotropic masses was of the same 

 character, and similar to that used by Pro- 

 fesser Boys. The conclusion reached, the ex- 

 perimental results being in agreement within 

 one or two-tenths of one per cent., is that 

 neither in the case of crystalline nor isotropic 

 masses was any deviation from the law of 

 Newton detected. The author fails to note 

 the very ingenious and interesting method of 

 attacking the problem of the attraction of 

 crystalltue masses proposed by Poynting in 

 his Adams Prize Essay on the Density of 

 the Earth. Poynting proposes to test the 



question of there being different proper- 

 ties as to attraction along different axes of 

 crystals by the directive action which must 

 exist when one sphere of a ciystal is in tlie 

 field of another. He made some experiments 

 along that line, and his work probably pre- 

 ceded by a year or two that of Dr. Macken- 

 zie. At the present moment, with library 

 out of reach, I am unable to say whether 

 he has published any further results. 



The Influence of Tenvperatxire on the Trans- 

 parency of Solutions, by E. S. Nichols and 

 Mary C. Spencer, is another prominent 

 article of the Review. Transparencj'^ to 

 various wave-lengths was tested and a num- 

 ber of color solutions were examined. There 

 are also papers on the Electric Conductivity 

 of Certain Salt Solutions, by A. C. Mac- 

 Gregorj', a continuation of the paper on 

 Forces between Fine Solid Particles totally 

 Immersed in Liquids and among the minor 

 contributions is one interesting and useful 

 on the Variation of Internal Eesistance of a 

 Voltaic Cell with Current, by Professor 

 Carhart. T. C. M. 



NEW BOOKS. 



Die Chemie des Chlorophylls. L. Marchlew- 

 SKi. Hamburg und Leipzig, Leopold 

 Voss. 1895. Pp. iv + 82. M. 2. 



Les Aurorespolaires. Alfred Angot. Paris, 

 Felix Alcan. 1895. Pp. vii + 315. 



Lehrhuch der Allcjemeinen Psychologic. Jo- 

 hannes Rehmke. Hamburg und Leipzig, 

 Leopold Voss. 1894. Pp. 582. M. 10. 



Iowa Geological Survey, Vol. III. Des Moines, 

 Published for the Iowa Geological Survey. 

 1895. Pp. 501. 



Magnetismus und Hypnotismus. G. W. Gess- 

 MAN. Vienna, A. Hartleben. 2d edi- 

 tion. Pp. xiv + 205. 



Bidletin of the Geological Institution of the Uni- 

 versity of Upsala. Edited by Hj. Sjogren. 

 Upsala, Almqvist & Wiksells. 1 893-1894. 

 Pp. 95, 293. 



