Sept. 15, 1 881] 



NATURE 



459 



Cave, which ought surely to belong to the chapter on the 

 " Recent Geological History of Yorkshire," only that the 

 latter happened to be written by one who confined him- 

 self to the Holderness drift. Under the head of "The 

 Permian Rocks " there is an exposition of the views of 

 those who would reintroduce the old (not recently sug- 

 gested) name Poikilitic to include the Trias. It was a 

 pity the author was not acquainted with any recent papers 

 on the series above the Lias, for there are no good boulders 

 in this part of the book. iVlr. Hudleston's admirable 

 papers on the Yorkshire Oolites seem to have been written 

 in vain, and there have been modern papers also on the 

 Yorkshire Chalk. It was perhaps excusable for our 

 author to conclude that the third edition of Prof. Phillips' 

 "Yorkshire Coast " contained all the most recent infor- 

 mation, though every East- Yorkshire geologist knew that 

 it did not. In examining a work on local geology it 

 is always well to see where the author lived, for the 

 surrounding country will be the best described. So it is 

 here; the best part of the book is the description of the 

 Middle and Upper Coal-measures, which are well deve- 

 loped in the neighbourhood of Bradford. For East 

 Yorkshire and the coast the book is of little value. 



The topography of the map requires no other guarantee 

 than the name of the constructors for its excellency. The 

 south-western part of the geological colouring derived 

 from the Geological Survey maps is also very good. Nor 

 can we complain when lack of published material pre- 

 vents accuracy elsewhere, though it is a reason for re- 

 gretting the slow publication of the Geological Survey 

 maps which have been long ago completed ; but when 

 the whole of the Vale of Pickering is coloured Neoco- 

 mian, and a patch of the same is placed in the south near 

 Cave, scarcely an acre of rocks of that age being dis- 

 coverable in the former, and none in the latter locality, one 

 is led still more to regret that the author's map should be 

 spoiled by his not knowing Mr. Hudleston's papers and 

 rel)ing on Prof. Phillips. But he has surely introduced 

 a little mistake of his own, which will be very serious to 

 visitors to the popular watering-places of Scarborough 

 and Filey. The Castle Rock and Filey Brig are coloured 

 — one Lower Oolite and the other Neocomian, whereas 

 they are both what the author would call " Middle 

 Oolite"! It will take more than Mr. Bird to write a 

 good " Geology of Yorkshire." 



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 inanuscripts. 

 No notice is taken of anonymotis communications. 



[ The Editor urgaitly requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible othenuise to ensure the appearance even 

 of communications co>!taining interesting and ncvel facts.\ 



Leaves Injured at Night by Free Radiation 

 Fritz Muller, in a letter to me from Sta. Catharina in Brazil, 

 dated August 9, supports the view which I have advanced with 

 respect to leaves \ lacing themselves in a vertical position at 

 night, during their so-called sleep, in order to escape being 

 chilled and injured by radiation into the open sky. He says : 

 " We have had last week some rather cold nights (2° to 3° C. at 

 sunrise), and these have given me a new confirmation of your 

 view on the meaning of the nyctitropic movements of plants. 

 Near my house there are some Pandanus trees, about a dozen 

 years old ; ihe youngest termi .al leaves stand upiight, whereas 

 the older ones are bent down so as to expose their upper surfaces to 

 the sky. These young leaves, though of cour.se the most tender, 

 are still as fresh and green as before ; on the contrary, the older 

 ones have suffered from the cold, and have become quite 

 yellowish. Again, the leaves of Oxalis sepium were observed 



by me to sleep in a very imperfect manner during the summer, 

 even after the most sunny days ; but now, in winter, every leaflet 

 hangs down in a perpendicular position during the whole night." 

 It is a new fact to me that leaves should sleep in a more or less 

 perfect manner at different seasons of the year. 



Charles Darwin 



Red Rainbows 



The account in Naturf, vol. xx'v. p. 431, of a pink rainbow 

 feen from Mr. Tennyson's houfe, recalls to me a rainbow- which 

 I witnesed in July 1877 over the Lake of Lucerne from the 

 promenade in front of the Schweitzerhof. The tow in question 

 appeared at s^unse', when the whole sky, east and west, was lit 

 up with ruddy tints ; and just tefore it faded cut, the bow it>elf, 

 which was a very brilliant one, showed only red and orange 

 colours in place of its usual array of hues. No fewer than five 

 supemumer.ir>' rrcs were visible at the inntr edge of the primary 

 bow, and these showed red only. I frncy that the phenr menrn 

 cannot be very raie, from the circumstance that in pictures of the 

 rainbow red and yellow are frequently the only colours set down 

 by the artist. A few months ago Mr. C. Brocke Branwhite of 

 Clifif n showed me a very beautiful sketch in oils ly his father, 

 the late Mr. Charles Branwhite, a colourist of ro mean power, 

 in which a be.-iutiful and exquisitely pellucid rainbow w-as drawn 

 with red and yellow tints only. It may aho be mentioned that 

 in the copy of Rafael' .> "Madonna di Foligno " in the Dresden 

 Gallery, there is a femi-circular red and yedow rainbow. I have 

 not seen the original Foligno Madonra in Rome; and should be 

 interested to know whether in this also red and yellow are the 

 only tints accorded by the colourist. 



Haslemere House, Clifton Silvanus P. Thompson 



In your issue of the 8th inst. (vol. xxiv. p. 431) your corre- 

 spondent "A. M." describes what he calls a " pink rainbow " 

 seen by him .it Aldf orth, near Hash mere, and as a painter I 

 am interested in his description, as it exactly correspords with 

 the same phenomenon as seen by me here, same date, and 

 viewed with curiosity by myself and friends. 



Corrie Hotel, Arran, September n David Murray 



Atoms 



Although I am not an "eminent" authority, perhaps you 

 will excuse my troubling you with the following extract from a 

 paper read by me before the Philosophical Society of Glasgow in 

 November, 1875, a coj y of which pnper I posted to the Editor 

 of Nature: — "I have long been of oj inion that the most 

 probable hypothesis of the origin of atoms is that there is only 

 one kind of matter — ether or its constituents — and that atcms 

 are merely congeries of units of ether circling at enormous speeds 

 round each other, differently grouped, in different numbers, at 

 different velocities, and at different distances, even as the dif- 

 ferent members of our sun systems. . . . The numbers of units 

 in each similar atom need not be aUv.iys the same ; a few 

 dozens more or less will not be appreciable by us. On the 

 other band, if a so-called element show a plurality of spectro- 

 scopic lines or hues, I do not think it at all doubtful that 

 there is a plurality of units moving to produce these, since 

 they thus show effects of different modes of moving of bodies ; 

 all our different states of sensual consciousness of colours are 

 necessarily dependent on differences in the modes of moving of 

 the agents that excite in us such plurality of lines and hues. 

 As the motions of atom , or rather of groups of atoms, excite 

 in us sensations of sound, so the motiors of units, or rather 

 of groups of units, excite in us sensations of colour, and 

 of course the lower-pitched movements of dark heat. Then 

 again, we may hold that the more lines that persist in a 

 spark or a sun, the less easily reducible are the portions of the 

 elements showing them, as far as these lines' constituents are 

 concerned — the lines being still undissociated material." (Proc. 

 Phil. Soc. of Glas., vol. x. p. 61.) Henry Muirhead 



Cambuslang, August 26 



Luminous Phenomena on Rupture of Sea-Ice 



In my diary for January 20, iSSi, occurs the following 

 passage. I make no attempt to account for the phenomenon, 

 but am certain it was not caused by any reflection of the lights 

 on board the vessel : — 



