6o4 



NA TURE 



[October 15, 1908 



endemic species of tlie genus, also of a peculiar 

 liliaceous epiphyte, AstcMa monfana. As character- 

 istic plants of the Solomon Islands there are figured 

 the epiphyte Polypodiuni quercifolium, an expanse of 

 " alang-alang " grass, Imperata arundinacea, and a 

 huge specimen of Calophyllum inopliyllum growing 

 close to the sea. A fine photograph of the stilt-roots 

 of a Ficus is contained in this part. Mr. E. Ule has 

 contributed the photographs from the " campos " in 

 the Brazilian State of Bahia., Various cactus plants 

 are illustrated, also some of the abundant 

 leguminous trees. The cluster of palms, Copernicia 

 cerifcra, the species yielding Carnauba wax, forms an 

 imposing group. The number devoted to the .Algerian 

 Sahara is also a xerophytic study. The plates in- 

 clude representations of Limotiiastruni Fcei, Arisfida 

 ptingens, and Pistacia terehintlius. In the final 

 double number Dr. Schenck presents some excellent 

 studies of plants in the Swiss and Tyrolese Alps. 

 The photographs that more particularly evoke admira- 

 tion are those showing cushions of Androsace 

 helvetica, flowers of Ranunculus alpestris, clumps of 

 Thlaspi rotuiidijolia, and straggling plants of Salix 

 retusa. 

 British Rainfall, 1907. By Dr. H. R. Mill. Pp. 100 



+ [280]; with maps and illustrations. (London: 



E. Stanford, 1908.) Price 105. 

 This excellent work, which has now reached its forty- 

 seventh annual volume, has, by the energy and ability 

 of its founders, established for itself a unique position 

 among general rainfall publications. It deals with 

 the distribution of rain in space and time over the 

 British Isles during the year 1907, as recorded by 

 more than 4000 voluntary observers, and is supple- 

 mented by articles upon various branches relating to 

 that subject. As it has appeared in practically the 

 same form for many years (which is a great advan- 

 tage for the purpose of reference), there is little to 

 be said about it that has not been previously men- 

 tioned ; the work of the British Rainfall Organisation 

 is continuallv expanding, and the author receives no 

 pecuniarv assistance in the onerous labour of prepara- 

 tion and publication of the report beyond some sub- 

 scriptions -from persons interested in rainfall work. 



Among the articles we may specially refer (i) to 

 an interesting discussion of the typical thunder- 

 storms of Julv 21-22, showing distinctly the linear 

 arrangement of heavy rainfall in such storms and its 

 disregard of the configuration of the land, and (2) 

 to an instructive note on mapping rainfall. The dis- 

 cussions of droughts and rain spells, and the monthly 

 and seasonal charts illustrating the rainfall of the 

 year, are also of exceptional interest. 

 Arbeiten aus dem Gebiet der expcrimentellcn Physi- 



ologie. By Dr. Hans Friedenthal. Pp. xi-f-4q3. 



(Jena : G. Fischer, 190S.) Price 8 marks. 

 This is a collection of fifty-five papers written either 

 by Dr. Hans Friedenthal or by the workers in his 

 laboratory. Dr. Friedenthal does not appear to have 

 any university or other oflicial post, but is the happy 

 possessor of a private laboratory at Nicolassee, near 

 Berlin, and he seems to be a prolific and versatile 

 worker. The first paper of the collection is an ob- 

 stetric one, written in 1894, but subsequently the 

 various branches of physiological investigation appear 

 to have had greater attraction for him, and he has 

 produced since that time publications dealing with 

 such subjects as absorption, immunity, digestion, 

 colloids and ions, cardiac and sympathetic nerves, 

 cancer, syphilis, the urine, and histological methods. 

 The papers themselves are of considerable interest, 

 and the collection is one of which any investigator 

 may well be proud. 



NO. 2033, VOL. 78] 



LETTERS TO THE EDITOR. 



[The Editor docs not Itold himself responsible for opinions 

 expressed by Itis correspondents. Neither can he tindertaize 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taiu^n of anonymous conimunicatio}is.] 



Observations on the Active Deposit of Radium in 

 Mid-ocean. 



In the month of May, 190S, by the kindness of the 

 captain and officers of the ss. Lake Erie, observations were 

 made between Montreal and Liverpool on the radio-active 

 matter collected on a negatively charged wire exposed to 

 the air for three or four hours. The wire was insulated 

 by ebonite rods, suspended from the flag halyards, and 

 charged by a Zamboni dry pile. .After exposure it was 

 coiled on a skeleton reel and placed in an electroscope 

 clamped to a board, together with the observing microscope. 

 There was no dilliculty in obtaining satisfactory readings, 

 in spite of the slight motion of the ship. 



The results obtained in mid-.\tlantic appear to approxi- 

 mate to those found in Canada or in England, but it must 

 be remeinbered that the amount of active deposit determined 

 at any given locality is liable to considerable variations. 



To an arbitrary scale, after deducting the natural leak, 

 the measurements of the active deposit were as follows : — 



May 5. Montreal 34 



,, b. „ 26 



,, 14. Ocean, lat. 50°, long. 45° 21 



,, 15- .. .. 52°. .. 3»° 64 



,, 16. ,, ,, 54°, .. _ 3°° 41 



July I. Hornsea, E. Yorkshire Coast ... 28 



„ 2. .. .. „ So 



,, IS- '. .^ .' 55 



,, 20. ,, ,, ,, 60 



,, 22. ,, ,, ,, 48 



Aug. 22. Seascale, W. Coast, Cumberland ... 30 



„ 24. ,, ,, „ ... 270 



The large value at Seascale on August 24 was obtained 

 Dn a vertical wire well exposed to a strong west wind. 

 The small values at Montreal resulted from a horizontal 

 wire on the roof of a house. An uncharged wire at sea 

 gave no result. 



These experiments, so far as they go, indicate that the 

 active deposit due to radium is prevalent to nearly the same 

 extent over land and sea. Observers have also found that 

 the ionisation of the atmosphere, measured by Ebert's 

 apparatus, is nearly the same over the ocean and over 

 the land. 



We may deduce, then, that in mid-ocean the radium 

 emanation, which decays to half value in 3-8 days, and 

 gives rise to the active deposit, cannot be entirely wind- 

 borne from the land, but that the emanation enters the air 

 from the ocean somewhat as from the ground. 



This is contrary to expectation, for the average number 

 of grams of radium per c.c. of rock is about 3-5x10-'^ 

 (Strutt) and per c.c. of sea water 3X10-" (Joly). It is, 

 however, probable that the emanation due to radium in 

 solution in sea-water escapes more readily than the greater 

 quantity generated in soil or rock. The emanation per 

 c.c. in the atmosphere near the earth's surface would be 

 in equilibrium with about 6X10-" grams of radium. 



Montreal, September 22. A. S. Eve. 



The Indigo Question. 



In an admirable article, " A Contribution to the Indigo 

 Question," which appeared in Nature of July 30 (p. 296), 

 Prof. Meldola discusses the report of the work carried 

 on by Messrs. Bloxam, Wood, Orchardson, Gaunt, and 

 Thomas in the clothworkers' laboratory at Leeds Uni- 

 versity, and agrees with the authors in the opinion they 

 express that there is still scope for considerable improve- 

 ment in the manufacture of natural indigo. On the other 

 hand, the general secretary of the Bihar Planters' Associa- 

 tion (Mr. T. R. Filgalt), in replying to this article 

 (Nature, October i), makes the remarkable statement, 

 " nothing further can be done in improving the main 

 processes." 



