222 



NA TURE 



[July 9, 1903 



LETTERS TO THE EDITOR. 



\The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or auy other part of Nature. 

 No notice is taken of anonymous communications.] 



Radium and Solar Energy. 

 The extraordinary discovery that radium has the property 

 of continuously radiating heat without itself cooling down 

 to the temperature of surrounding objects may possibly 

 afford a clue to the source of energy in the sun and stars. 



Taking the Curies' observation that one gram of radium 

 can supplv loo calories per hour, I thought it would be of 

 interest to compute how much radium would suffice to 

 supply the sun's output of energy. 



Taking from Langley's observations that this is equal to 

 828,000,000 calories per square cm. per hour, I find that 

 3-6 grams of radium per cubic metre of the sun's volume 

 would supply the entire output. 



It may be possible that at solar temperatures radium is 

 capable of much more energetic radiation, and, if so, the 

 36 grams might be reduced to a much smaller figure. 

 Daramona, July i. W. E. Wilson. 



"Red Rain" and the Dust Storm of February 22. 



In a letter under the above heading which you did me 

 the honour to print in your issue of May 21, vol. Ixviii. 

 p. 53, I gave the results of the chemical examination of a 

 sample of dust collected from the roof of Bayham Abbey, 

 Lamberhurst, after the dust storm of February 22, and sent 

 to me by the kindness of Lord Camden, and I stated that 

 it would be interesting to compare its characters with those 

 of the dust, presumably of African origin, which was 

 observed to fall in the district of Taormina by Sir Arthur 

 Rticker, and was the subject of an interesting communica- 

 tion to Nature by Prof. Judd in 1901 (vol. Ixiii. p. 514). 



Thanks to the kindness of Prof. Judd, who sent me about 

 a gramme of the Taormina dust collected by Sir Arthur 

 Riicker and placed among the geological specimens at 

 South Kensington, I have been enabled to make the com- 

 parison. 



In external characters the Taormina dust closely re- 

 sembles that from Bayham Abbey. Its microscopical 

 features are also generally similar. 



Mr. C. Simmonds, of the Government Laboratory, to 

 whom I am indebted for the analyses already published, 

 found that after drying at 100° C, the sample had the 

 following composition : — ■ 



Per cent. 



Silica 3632 



Alumina 16-35 



Ferric oxide, with traces of manganese oxide 608 

 Cobalt oxide ... ... ... ... ... 032 



Lime ... ... ... ... ... ... 6-24 



Magnesia 221 



Sodium oxide ... ... ... ... ... 2 59 



Potassium oxide ... ... ... ... 2 72 



Water and organic matter 2349 



Chlorides and sulphates traces 



Carbonic acid ... ... ... ... ... 3 68 



The cobalt oxide may include a little nickel, but the 

 quantity was too small to identify with certainty. 



After being heated to redness, 2808 per cent, of the 

 sample was dissolved on boiling with dilute hydrochloric 

 acid, the soluble constituents being : — 



Per cent. 



Silica 088 



Alumina ... ... ... ... ... ... 10 16 



Ferric oxide 552 



Lime 624 



Magnesia ... ... ... ... ... 2-21 



Alkalis 257 



Carbonic acid (by difference) ... ... ... 0-50 



2808 



The organic carbon in the sample amounted to 989 p6r 

 cent., and the organic nitrogen to 016 per cent. This 



NO. T758, VOL. 68] 



small proportion of nitrogen shows that the organic matter 

 is mainly, or entirely, of vegetable origin. Calculated from 

 the mean proportion of carbon in cellulose and humic acid, 

 the amount of organic carbon present in the sample would 

 correspond to about 19 per cent, of organic matter, or, from 

 cellulose alone, to 163 per cent. 



A comparison of the dust from Taormina with the " red 

 rain " dust from Bayham Abbey may be made by calculating 

 the inorganic constituents as percentages on their sum, 

 after deducting water and organic matter :— 



loooo 100 00 



Reduced thus to a common basis for comparison, the 

 inorganic portions of the two samples show a general 

 similarity of composition, the chief differences being that 

 the Bayham Abbey specimen contains a little more silica 

 and chalk, and a little less alumina and alkalis, than the 

 sample from Taormina. 



The constituents soluble in dilute hydrochloric acid may 

 similarly be compared, after deducting carbonic acid and 

 raising the figures to percentages : — 



It is of interest to compare the foregoing results with 

 an old analysis by Gibbs of dust which fell on a ship 

 in the Atlantic (Pogg. Ann., Ixxi., 367). After deducting 

 18.53 Psr cent, of water and organic matter, the composition 

 was found to be as follows : — 



Per cent. 



Silica 45-58 



Alumina ... ... ... ... ... ... 2055 



Ferric oxide ... 939 



Manganic o.xide ... ... ... ... ... 4-22 



Calcium carbonate ... ... ... ... 11-77 



Magnesia 2-21 



Potash ... ... ... ... ... ... 364 



Soda 233 



Cupric oxide 031 



Except for the presence in this sample of a notable quan- 

 tity of manganese and copper, the analysis bears a close 

 resemblance to that of the Taormina dust ; the fact of the 

 similarity is particularly interesting, considering that some- 

 thing like half a century has probably elapsed since Gibbs 's 

 sample was collected. 



Mr. J. J. H. Teall, the director of the Geological Survey, 

 kindly sent me a sample of " blood rain " dust which fell 

 at Palermo at about the same time as the dust from Taor- 

 mina collected by Sir Arthur Riicker. This closely re- 

 sembles the Taormina dust in general characters. Mr. 

 Teall has suggested that the question of the origin of the 

 dust might be elucidated if the samples were found to 

 contain free aluminium hydroxide. The bearing of this 

 upon the question of origin is as follows : — Evidence has 

 been recently adduced to show that laterite, a decomposition- 

 product of the felspars, is an aluminium hydroxide, though 

 always mixed with more, or less silica. This type of de- 

 composition, it is believed, occurs only in tropical regions, 

 and hence the presence of uncombined alurnina in the dust. 



