September 6, rgo6] 



NA TURE 



473 



One of the most important collections of plants in recent 

 years was collerted by Mr. K. M. Wilson, chiefly in western 

 China, for Messrs. James Vcitch and .Sons. A few of the 

 men' striking new species are describi'd in the Kc-t' liiiltctin, 

 ><'o, 5. Three species of Berberis, a new genus Hosiea 

 under the order Icacine;e, and some roses are among the 

 jumiber. Sir George Watt contributes an interesting article 

 «n Burmese lacquer-ware and varnish, the basis of which 

 is the oleo-resin, ihit-si, of Melanorrhea usitata. Less 

 generally known than the Pagan and Prome lacquer boxes 

 :and trays is the Mandalay moulded lacquer; the resin, 

 thickened with ground rice husk, furnishes a material 

 suitable for modelling figures and ornamentation in relief. 

 Mr. C. H. Wright continues his diagnoses of new African 

 plants, and Mr. J. H. Hellier identifies the Eben tree of 

 Old r.ilabar as Pmhylohtis ediilis. 



I\ a forest survey the e.samin.ition and measurement of 

 selected plots provide data for working plans. A more 

 <letaile;d study of certain plots in a forest reserve on the 

 island of Luzon with the object of investigating the origin 

 of the different types of vegetation is being undertaken by 

 Mr. W. H. Whitford, who has published the first part of 

 his account in the Philippine Journal of Science, vol. i., 

 No. 4. Even here disturbances caused by human agency 

 have to be taken into account. The natives clear the land 

 for cultivation, but leave the clearings after a while, when 

 they change to grass-land or revert to forest. Again, 

 where the timber has been ruthlessly cut out or burnt, only 

 brushwood mi.xed with trees of invading species is left. 

 For such a type of vegetation the writer adopts the term 

 parnni;, distinguishing the parang according to the 

 <loTnin:mt tree or trees. 



A FORMULA giving the influence of frequency upon the 

 «elf-inductance of coils is discussed by Mr. J. G. Coffin in 

 the Proceedings of the American Academy of Arts and 

 Sciences, xli., 34. The formula itself involves hyperbolic 

 functions, hut the author shows by means of curves that 

 the results for large or small frequencies can be given with 

 fiufficient accuracy by simple approximations. 



In a short paper in the Verhandhingen of the German 

 Physical Society, Prof. F. Kohlrausch suggests the use of 

 the term " resistance capacity " as applied to the space 

 between two electrodes to denote the resistance of that 

 space when filled with a medium of unit electrical conduc- 

 tivity, and he shows how this quantity is related to the 

 capacity of a condenser the dielectric of which occupies the 

 space in question. 



Dr. Joseph Nabl, of Vienna, contributes to the Natur- 

 ■wissenschaftliche Rundschau an article written for the 

 purpose of explaining in simple language the meaning of 

 the second law of thermodynamics and its connection with 

 the theory of probability (Boltzmann's minimum theorem), 

 as well as the notion of entropy and the properties associ- 

 ated with it. The account is probably as good a one as 

 could be given in so limited a space for the instruction of 

 non-mathematical readers. 



In the Proceedings of the American Academy of Arts 

 and Sciences, xli., 32, Mr. Harvey N. Davis discusses the 

 longitudinal vibrations of a rubbed string. Instead of 

 basing the investigation on the use of Fourier's series as 

 was done by Helmholtz in his well-known investigation of 

 the vibrations of a violin string, Mr. Davis makes use of 

 the graphic methods which have been commonly employed 

 by mathematicians in discussing the impact of elastic 

 beams. It appears both from theory and experiment that 



^o. 923. V .,. 4 1 



the envelope of a string which is rubbed either transversely 

 or longitudinally at an aliquot point i/fe of its length is 

 not Helmholtz's parabola, but k chords inscribed in that 

 parabola — a result which strikes the reader as being, on 

 the face of it, in accordance with common sense. A 

 number of other results, such as the verilicalion of Krigar 

 Menzel's law, have been discussed. 



Vol. iii., No. 2, of Investigations of the Departments 

 of Psychology and Education of the University of Colorado 

 contains several interesting papers. Under the title " Pro- 

 portion as the Quotient of Two Forms of One Equation," 

 Mr. Heman Burr Leonard suggests certain new methods 

 of teaching problems in proportion, and if these do not 

 look quite so simple on paper as they really are, the 

 article certainly confirms an important point, namely, the 

 necessity of familiarising pupils with the use of formulae 

 in solving problems, instead of the more restricted methods 

 of " rule of three." Under the title " Relation of Course 

 of Study to Higher Wages " Prof. John B. Phillips directs 

 attention to the large number of important inventions that 

 have been made by men of little or no education. His 

 suggestion that " invention " should form part of an educa- 

 tional curriculum is interesting, though one may perhaps 

 ask whether teaching people to be original is not rather a 

 contradiction of terms. Lastly, we have an account of the 

 Colorado Mathematical Society, founded last year, from 

 which it appears that several important points in the 

 teaching of mathematics, such as over-elaboration of text- 

 books, athletic and other distractions, and what has some- 

 times been called " spoon feeding " on the part of teachers, 

 have been discussed. 



Mr. R. J. TiiOMrsoN deals with the development of 

 agriculture in Denmark in a paper published in the Journal 

 of the Royal Statistical Society, Ixix., 2. He attributes 

 the prosperity of the country to three causes : land tenure, 

 education, and cooperation. So far from rural depopula- 

 tion taking place, the land is better farmed than it was 

 forty years ago. The rate of wage is lower than in 

 England, and thrift is a national characteristic. The bulk 

 of the land is cultivated by the owners in small farms. 



About forty years have elapsed since Gustav Theodor 

 Fechner laid down his principle of association. The 

 Psychological Review has marked the occasion in a fitting 

 way by devoting its May number to a paper by Prof. 

 Lilien J. Martin on an experimental study of Fechner's 

 principles of aesthetics. It is illustrated by a portrait of 

 Fechner and a coloured reproduction illustrating a case of 

 chromansEsthesia. 



The isolation and identification of radio-thorium from 

 the sediments of Bad Kreuznach is described in detail by 

 Messrs. Elster and Geitel in the Physikalische Zeitschrift 

 (\o. 13). The fact that radio-thorium is associated with 

 iron in these sediments suggested a simple method of 

 isolating radio-thorium from ordinary thorium salts. .A 

 nearly neutral solution of thorium chloride was mixed with 

 a solution of ferrous bicarbonate, when it was found that 

 the ferric hydroxide precipitated in the course of a few days 

 was highly active, .^fter removal of the iron, several 

 milligrams of a thorium hydroxide were obtained having 

 an activity twelve times that of the original thorium. 

 These results, taken in conjunction with those already re- 

 corded (N.iTURE, vol. Ixxiv., p. 385), leave little doubt that 

 thorium owes its activity to radio-thorium. 



Despite the many attempts which have been made to 

 elucidate the nature of the blue substance formed by the 

 action of iodine on starch paste, the question still remains 



