February i8, 1909J 



NA TURE 



457 



hampered in their endeavours by the difficulty of 

 identifying the particular liind of noxious serpent witli 

 whicli they may be called upon to deal. If is largely 

 with the view of supplying a ready method of making 

 such identifications that the unpretentious work before 

 us has been presented to the public. That it has been 

 heartily appreciated is made evident by the fact of its 

 having reached a second edition, after the sale of a 

 first issue of 2500 copies. The author relies on the 

 arrangement, size, and number of the scales as afford- 

 ing the easiest clue to the identification of species, and 

 for this purpose gives figures of the scaling of certain 

 parts of the body or head of a considerable number of 

 the thirty-nine species recognised which in his opinion 

 render identification easy and certain. 



In the present edition the author has ventured to 

 recognise more species than are admitted in Mr. 

 Boulenger's volume in the " Fauna of British India." 

 He is of opinion, for instance, that under the name 

 of Ancistrodon hypnalc, two species — one from Ceylon 

 and the other from the Western Ghats — have been 

 confounded, while a new krait is recognised from 

 Assam, and the Biinganis candidiis of Boulenger is 

 split up into several species. In addition, Psciido- 

 cerastfs persiciis has recently been identified in British 

 India. Apart from the special purpose in connection 

 with snake-bite, the book is a useful and handy guide 

 to the Indian " Thanatophidia." R. L. 



Gray's Neiv Manual of Botanv. Re-arranged and ex- 

 tensively revised by B. L. Robinson and M. L. 

 Fernald. Seventh edition. Pp. 926. (New York : 

 .\merican Book Company, n.d.) 

 This well-known flora of the central and north-en<tern 

 parts of the United States of .America was originally 

 compiled in 1S4.S by Dr. Asa Gray, who was professor 

 of natural history in Harvard University. It has 

 passed through si.x editions, and has been revised three 

 times, the last revision having been undertaken by 

 Dr. S. Watson and Prof. J.^ M. Coulter in iSoo'. 

 .■\nother edition had become desirable if only to bring 

 the book into conformity with the pronoimcements of 

 the International Botanical Congress at Vienna, and no 

 more opportune occasion was likely to arise for carry- 

 ing out at the same time the practically inevitable 

 displacement of the arrangement of Bentham and 

 Hooker's " Genera Plantarum " by the more modern 

 system elaborated by Dr. Engler. These sweeping 

 reforms have been effected by the new editors, who 

 are botanical professors at Harvard University, and 

 therefore officially entitled to prepare the flora, of 

 which the copyright is held by the university. 



The authors have also modified the geographical 

 limits covered by the manual, whereby certain terri- 

 tories in the west are excluded, and considerable areas 

 in Quebec, Ontario, and other Canadian provinces are 

 included. The changes do not by any means end 

 here ; practically the arrangement of every important 

 family — to use the word officially recommended for the 

 group, better known as an order — and every large 

 genus has been re-cast, so that the title of the book 

 has been advisedly qualified. The assistance of 

 specialists has been obtained for the descriptions of the 

 grasses, orchids, Crat^gus, and a few other genera. 



The flora is confined to Pteridophyta and Spermato- 

 phyta ; there is a considerable increase in the total 

 number of species, that now exceeds four thousand. 

 Under the genus Panicum, seventy-three species are 

 distinguished, and under Carc.x as many as a hundred 

 and eighty-five. The forms of Crataegus, a species 

 that is highly vari.-ible in America, are brought under 

 sixty-five species by Mr. \\'. W. Eggleston. 



Undoubtedly the revision will be cordiallv welcomed 



NO. 2051, VOL. 79] 



by botanists, and should prove especially useful to 

 botanical workers in south-eastern Canada. The ad- 

 mirable series of analytical keys that were a feature 

 of the older editions have been maintained, and 

 further help is given for difficult genera in the shape 

 of small illustrations, by the side of the text, of those 

 parts of the plant that furnish diagnostic characters. 



The New Word. By Allen Upward. New edition. 



Pp. 317. (London : A. C. Fifield, 190S.) Price 55. 



net. 

 Scientific Corroborations of Theosophy : a Vindication 



of the Secret Doctrine by the Latest Discoveries. 



Bv Dr. A. Marques. Revised and greatly enlarged 



edition. Pp. iv+ 152. (London : The Theosophical 



Publishing Society, 1908.) Price 2s. 6d. net. 

 Mr. Allen Upward describes his book as " a plea 

 for reason against authorit)'," and proceeds to discuss 

 a number of problems of modern science from a 

 layman's point of view. Men of science will approve 

 the spirit in which Mr. L^pward writes, even if they 

 remain unconvinced by his arguments. 



Readers will discern from the title to his book the 

 line of thought which characterises the volume of 

 Dr. Marques. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opiniom 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



The Boiling Point of the Radium Emanation. 



It was shown by Rutherford and Soddy in 1903 that the 

 radium emanation was condensed from the gases with 

 which it was mixed at a temperature of about —150° C. 

 From observations of the range of temperature of condensa- 

 tion and volatilisation it was concluded that the condensed 

 emanation exerted a sensible vapour pressure. This has 

 been confirmed by later experiments, using much larger 

 quantities of emanation. Sir William Ramsay and 

 Cameron have pointed out that the emanation, condensed 

 in a glass tube liept at the temperature of liquid air, can 

 be removed by continuous pumping, thus indicating 

 appreciable vapour pressure even at that low temperature. 

 I have found that the rate of removal of the emanation in 

 this way increases rapidly as the temperature of complete 

 volatilisation is approached. 



In the initial experiments of Rutherford and Soddy onfy 

 very small quantities of radium were available, and the 

 partial pressure of the emanation in the experiments was 

 exceedingly small. If the emanation behaves like an 

 ordinary gas, it is to be expected that the boiling point of 

 pure emanation at atmospheric pressure should be much 

 higher. I have recently made experiments to test this 

 point. As the volume of pure emanation available in the 

 present experiments was only about 1/20 cubic millimetre 

 it was necessary to employ special methods to investigate 

 the boiling point of the emanation at various pressures. 

 Purified emanation corresponding to the equilibrium 

 amount from about 100 mifligrams of radium was com- 

 pressed into a fine glass capillary of about 1/20 millimetre 

 diameter. The end of the capillary dipped into a pentane 

 bath, which was cooled down to any desired temperature, 

 measured by means of a thermocouple. The point of initial 

 condensation was marked by the appearance of a brilliant 

 point of phosphorescent light, due to condensed emanation, 

 at the coldest part of the capillary. In this way I have 

 found that the temperature of initial condensation of the 

 emanation rises from about —150° C. at a very low 

 pressure to about -65° C. at atmospheric pressure. This 

 fixes the boiling point of the emanation at atmospheric 

 pressure at about -65° C, or 208° absolute. 



