;96 



NA TURE 



[February 21, 1901 



contained in my edition of Lummer's book — slips for which I take 

 the entire responsibility. The error on p. lOO in supposing 

 that the Munich view was photographed by Prof. Miethe, of 

 Berlin, arose from a confusion between two sets of telephoto- 

 graphic views sent me from Germany, some of which were taken 

 by Prof. Miethe. I would point out that, in the only case in 

 which the kind of lens used is stated, it is correctly stated to be 

 a Steinheil's lens. I presume Dr. Steinheil is not dissatisfied 

 with the performance of the lens in producing the picture, by 

 whomsoever it was photographed. The other point arose from 

 inserting at the last moment, when the sheets were going to 

 press, a reference to Messrs. R. and J. Beck, which should have 

 been inserted at the end of paragraph four instead of paragraph 

 three of Chapter xi. Let me assure Dr. Steinheil that both 

 points will be corrected in any fresh issue of the text. 



February 9. Silvan us P. Thompson. 



The Ash Constituents of Some Lakeland Leaves. 



Although it cannot be maintained that the amount of 

 inorganic matter which the leaves of a tree extract from the soil 

 on which it grows is quite independent of the chemical com- 

 position, &c., of that soil, it was deemed advisable to perform a 

 few experiments bearing on this particular feature. Notwith- 

 standing the considerable elevation, viz. about 400 feet, the soil 

 in this locality is distinctly suited and adapted to the growth 

 and healthy development of most of our well-known forest trees. 

 It is a cold, basic clay, mostly not very stiff, on account of the- 

 presence of some gravel and peat in many places, and, generally 

 speaking, enriched with considerable quantities of potash, 

 silica and manganese, while a serious deficiency in lime is 

 attested by the universal prevalence of distinctly calcifuge 

 plants. The percentage of crude ash set down in the subjoined 

 table was calculated from the combustion of the leaves gathered 

 in the evening, dried first in the air and then at 100° C. The 

 details are as described : — 



The steady increase in the quantity of ash in the leaves of 

 sycamore and wych elm as the season progresses is here 

 exhibited with sufficient emphasis. The peculiarity, however, 

 is that in the case of the sycamore the percentage does not 

 reach the figure that it might do on other soils or under other 

 circumstances ; for instance, according to Schleiden and 

 Schmidt, it might come up to 28 per cent.; but this proportion, 

 I make bold to say, is never attained in any part of British 

 Lakeland. The surprisingly large percentage of silica and lime 

 in the ash of the deep crimson leaves and petioles of the rowan 

 demands further investigation, inasmuch as this is a rather 

 calcifuge tree, and the amount of silica in other allied Rosaceans 

 is very small. According to RismuUer, the ash of dry beech 

 leaves is 4-6 percent, on May 7 and 11 -4 per cent, on November 

 18 ; whereas Gueymard found that when gathered after natural 

 fall and dried they yield only 5-6 per cent, ash, and my experi- 

 ments do not warrant the assumption of any serious difference 



NO. 1634, VOL. 63] 



as respects inorganic constituents between the vernal and 

 autumnal foliage of this tree. " Alone among the species of the 

 first order of Mid and North Europe," says MM. Fliche and 

 Grandeau, "the Scots pine seems to seek out siliceous soils, 

 but the physical rather than the chemical conditions of the soil 

 seem, as regards this species, to have a preponderant influ- 

 ence." Nevertheless, the percentage of ash in .its first and 

 second years' leaves is precisely the same here as it is in North 

 Germany, and the extremely moderate inorganic pabulum that 

 suffices to sustain it and the birch enables them to bear the 

 privations of an upland abode. P. Q. Keegan. 



Patterdale, Westmorland. 



An Earthquake on February 10. 



In the early hours of February 10, in the town of Grazalema, 

 there was experienced an intense earthquake, with damages to 

 buildings, many of them being rent. 



The duration was about three seconds, and the movement a 

 compound one of oscillation and trepidation, accompanied with 

 considerable noise. 



The people ran out of the houses full of terror. 



The church of Saint Joseph and some other large buildings 

 have been very severely damaged, and also factories and mills. 



The body of water that provided motive power for the 

 machinery in one of the factories has disappeared. 



Grazalema is a town of 10,000 inhabitants, situated in a hilly 

 district of the province of Cadiz, at about 70 kilometres, nearly 

 due north, from Gibraltar. Augusto Arcimis. 



Inslituto Central Meteorologico, Madrid, February 13. 



The late Prof. Hermite. 



Your interesting memoir of Prof. Hermite differs in one 

 detail from the account in " Men and Women of the Time." 

 It is said there that he was born at Dieuze, in Lorraine, and that 

 he was for a while at Nancy before going to Paris. 



W. B. C. 



TtiE RADIO-ACTIVITY OF MATTER. 



A T the commencement of the year 1896, in carrying 

 -^^"^ out some experiments with the salts of uranium, 

 the exceptional optical properties of which I had been 

 studying for some time, I observed that these salts 

 emitted an invisible radiation, which traversed metals 

 and bodies opaque to light as well as glass and other 

 transparent substances. This radiation impressed a 

 photographic plate and discharged from a distance elec- 

 trified bodies — properties giving two methods for studying 

 the new rays. 



The phenomenon does not appear to be influenced by 

 any known external cause, such as a variation of tempera- 

 ture or a luminous excitation ; it is entirely different 

 from phosphorescence ; is not weakened in an appreci- 

 able manner by time, even at the end of several years ; 

 and is emitted spontaneously without any apparent 

 exciting cause. The radiating property appeared, firstly, 

 to be bound up with the presence of the chemical 

 element uranium ; the metal discharges electrified bodies 

 three to four times faster than its salts. 



If some fragments of uranium or of one of its salts 

 are placed upon a photographic plate wrapped in black 

 paper or covered by an aluminium leaf, and if between 

 the uranium and the plate various substances are inter- 

 posed, there is obtained at the end of several hours or 

 days, radiographs showing that the radiation is propa- 

 gated in straight lines, and traverses different bodies un- 

 equally. In the radiographs the edges of the plates of 

 glass, or of thin plates of other substances, throw a sort 

 of shadow, which is stillunexplained. This phenomenon, 

 as well as an inequality obtained twice accidentally 

 through parallel and crossed tourmalines, led to the belief 

 at the commencement of these researches that these rays 

 had properties in common with light. But all the later 

 experiments have shown that the new radiation undergoes 

 neither reflection, refraction nor polarisation. 



