540 



NATURE 



[Oct. 4, 1888 



it is useful ; secondly, we have established the great principle of 

 " correlation of growth," which is a brief way of stating that in 

 organisms there is such an intricate binding together of the 

 mechanism that when one part varies other parts vary con- 

 comitantly — so that a useful variation of the beak or eyelid of a 

 bird (for example) may necessitate a concomitant and perfectly 

 useless variation in the toe-nails or the tail-feathers , thirdly, 

 useless structures undoubtedly exist owing to the potency of 

 heredity, which is of such strength that long after a structure has 

 ceased to be a matter of selection it is transmitted from genera- 

 tion to generation, though dwindled in size and more or less 

 imperfect in structure. 



I think there will be no difficulty by reference to one or other 

 of the three considerations above stated in disposing of cases of 

 so-called "uselessness," or "prophetic" functionless organs 

 " on the way to use," which the Duke of Argyll may find to be 

 stumbling-blocks in the way of his faith in Darwin, if he will 

 submit them one by one for pulverization, though I am afraid 

 the process will not interest your readers. 



September 31. E. Ray.Lankester. 



A Shadow and Halo. 



A FEW evenings ago, whilst walking down a sloping pasture, 

 with the moon shining brightly at an altitude of about 20° 

 behind me, and with no visible dew nor fog, yet with heavy 

 dew on the grass, I noticed that the shadow of my head and 

 shoulders was very sharply defined, but that it was surrounded 

 by a halo of light, and that this halo or nimbus increased in 

 brightness as my shadow was lengthened out because of the 

 increasing slope ; and not only was the brightness increased, 

 but it extended now to my hips. That this was due to the 

 greater depth of moist air through which the moon's light passed, 

 by reason of the increase of the slope, I think was proved by 

 the fact that in the neighbourhood of a high hedge, which 

 would to some extent alter the conditions, this halo nearly 

 wholly disappeared. At one time I thought that my eyes were 

 deceiving me concerning this appearance, the contrast of the 

 dark shadow with the surrounding brightly illuminated grass 

 giving rise to the appearance above mentioned, but, by holding 

 up my hand so as to cut off the view of the shadow, I still saw 

 the brighter light which surrounded it, and this brightness still 

 increased or decreased in intensity as the slope on which I took 

 up my position was greater or less. There was no casting of a 

 shadow on a fog-bank, as there was no fog at all, but rather 

 the air was particularly clear. I noticed this phenomenon three 

 nights in succession. I shall be glad to know if any other 

 amongst your readers has noticed this occurrence, and will 

 explain it. E. W. P. 



Tamworth, September 29. 



Sonorous Sands. 



Referring to Mr. Cams- Wilson's letter recording the sup- 

 posed discovery of musical sand in Dorsetshire, I may mention 

 that about two .years ago the late Admiral E. J. Bedford sent 

 me three boxes of musical sand, one of them being labelled, 

 "Musical sand; Studland Bay, Dorset, 1885 ; sonorous when 

 collected." I am not aware whether Admiral Bedford himself 

 discovered the sonorous properties of this sand, but it is clear 

 that he was well acquainted with both the sand and its character 

 in 1885. A. R. Hunt. 



Torquay, September 27. 



THE REPORT OF THE KRAKA TAO 

 COMMITTEE OF THE ROYAL SOCIETY. 



I. 



A FTER an interval which has been prolonged partly 

 ■*"*■ by the unexpected continuance of the subsequent 

 atmospheric phenomena, and partly through other circum- 

 stances incidental to publishing, the Report on the great 

 eruption of the volcanic island of Krakatab in August 

 1883 is now before the world. 



Every Committee is bound to issue a Report of some 

 kind, but it rarely falls to the lot of a Committee to deal 

 -with anything at once so stupendous in its character and 



far-reaching in its consequences as the eruption which not 

 only figuratively, but literally, vibrated through the world 

 on August 27, 1883. 



We, in these islands, may boast of our Essex earth- 

 quakes, and of the frequent little tremors to which a 

 certain district in Perthshire is subject ; but few of us, 

 or our immediate neighbours, can, from our local expe- 

 rience, form the faintest conception of the terrific sub- 

 terranean powers which ordinarily manifested themselves 

 in the volcanic region of which Krakatab may be fitly 

 termed the focus. 



The first accounts which reached us by telegram, in- 

 accurate though they were bound to be as regarded details, 

 were scarcely exaggerations in point of magnitude ; and, 

 indeed, the cataclysm in this case rose superior to all 

 artificial modes of transmission, by announcing the very 

 date and hour, if not minute, of its culminating explosion 

 through a series of air-waves, which recorded themselves 

 no less than four times on every automatically recording 

 barometer throughout the world. 



Three other distinct and abnormal phenomena were : 

 (1) the immense distance to which the sound-waves were 

 propagated (altogether transcending anything hitherto on 

 record ; (2) the immense local height, destructive power, 

 and subsequent wide diffusion of the accompanying sea- 

 waves, which in this case were not, as is usually the case, 

 due to earthquake action ; (3) the simultaneous occur- 

 rence in the Javan and Indian area, and subsequently 

 rapid extension, first round the equatorial zone, and, 

 finally, to the whole world, of a most remarkable group 

 of optical phenomena, including coloured suns, lurid and 

 prolonged glows at twilight, large corona? round the sun 

 and moon, and a peculiar cirriform haze which was 

 evidently connected in some way with these and the 

 eruption. 



It was plain, in the face of these preliminary facts, that 

 the collection and discussion of such a grand series of 

 exceptional phenomena gratuitously evolved out of 

 Nature's own laboratory, could not fail to be of service 

 to science, and that while the more local features and 

 practical results of the episode might be left to the Dutch 

 Government, to whom the district belonged, its attendant 

 and subsequent phenomena deserved permanent record 

 in the pages of scientific history. 



On this basis, a Committee of the Royal Society was 

 appointed on January 17, 1884, in the following terms : — 



" That a Committee, to consist of Sir F. Evans, Prof. 

 Judd, Mr. Norman Lockyer, Mr. R. H. Scott, General 

 Strachey, and Mr. G. J. Symons, with power to add to 

 their number, be appointed to collect the various accounts 

 of the volcanic eruption at Krakatab and attendant phe- 

 nomena in such form as shall best provide for their 

 preservation and promote their usefulness." 



The subsequent expansion of the Committee by co- 

 operation of additional members, and the substitution of 

 one — Captain Wharton — in consequence of the death of 

 Sir Frederick Evans, is detailed in the preface. 



The main object of the Committee was thus to collect 

 facts and reduce them into a systematic and useful form. 

 While this has been its primary object, it has been 

 thought advisable to enlarge upon the original basis of 

 the Report, and, while giving a resume 1 of all the leading 

 opinions, especially those relating to the debated question 

 of the relation of the optical phenomena to the eruption, 

 to enter at some length into a discussion of the facts thus 

 systematized. Though it is hardly to be expected that 

 everybody will agree with the deductions arrived at by 

 each author, and though it has been impossible to avoid 

 omissions in a work embracing, in its latter sections, 

 observations extending over three years, and a literature 

 of its own, the main facts have not only been recorded, 

 but, as the Chairman, Mr. G. J. Symons, says, can be 

 readily verified. 



