June 28, 19 17] 



NATURE 



345 



salts. The point is, as Prof. Cushny shows, that the 

 tubule cells always absorb a fluid of the composition 

 referred to, whatever may be the needs of the body at 

 the time. They have no power of choice. 



The new view must be welcome to those who wish 

 for simplification. It will probably not appeal to those 

 who hold that this is no advantage to a theory, at all 

 e%-ents in biology. W. M. Bayliss. 



University College, London, June i6. 



The expression "mere machine" is Prof. Cushny's, 

 not mine. One is glad to learn from Prof. Bayliss 

 that this is not to be interpreted too literally. We all 

 look forward to the time when the expression "vital 

 energy" can be expunged from our vocabulary, but 

 whether the "modern theory" helps us to the realisa- 

 tion of this ideal renewed research alone can show. 

 That Prof. Cushnv's theon,' is in the -direction of 

 simplification is a matter of opinion. 



The Reviewer. 



The Origin of Flint. 



Sir E. Ray Lankester (Nature, June 7) does not 

 say what form of carbon he refers to as the colouring 

 matter of black flints. If it be carbon, why is the 

 coloration not extended to the white cortex? The 

 blackest flint nodules I have seen occur in a chalk-pit 

 near Faversham, but the apparently black silica be- 

 comes white when powdered-, showing it to be merely 

 an optical effect. I believe that Judd was the first to 

 point this out, more than thirty years ago. I refer to 

 the flints obtained direct from the chalk and not to 

 those' which, having become dissociated from the 

 parent mass, have been afterwards subjected to the 

 influence of various solutions. 



The white zone on the exterior of a flint does not 

 necessarily indicate decompos'tion. In flints taken 

 direct from the chalk it is due to the fact that the rock 

 contiguous to the nodule has not been wholly silicified. 

 Sometimes nodules in the chalk are white throughout, 

 being formed entirely of soft, cryp to-crystalline silica, 

 the spaces between the quartz not being filled with 

 colloid silica. I have found these near Corfe. There 

 is no evidence of decompositiop, and I regard them as 

 representing an early stage in the forming of a flint 

 nodule. 



Some decomposed flint pebbles found at Southboume- 

 on-Sea, described bv me in Nature at the time (May i, 

 1890), are very similar in appearance, but these results 

 are due to deformation. 



Manv facts seem to- prove that flint has been formed 

 since the chalk became indurated and elevated. The 

 naturally repaired fractured flints found near faults, 

 etc., and the remarkable compound flints which 1 

 recently exhibited at the meeting of the Geol. Physics 

 Society, are instances. In some of the latter speci- 

 mens there are as many as four thick deposits of flint 

 surrounding the original nodule, and as there appears 

 to be little, if any, mojecular continuity between the 

 layers, the growth of the compound nodule must have 

 been arrested from time to time during its develop- 

 ment in the solid chalk. Cecil Carus-Wilson. 



The suggestion of Dr. R. M. Caven (p. 306). that 

 the black colour of flint is due to ferrosoferric oxide, is 

 supported by the fact that flints which have been for 

 some time in contact with gas-lime (as when a mixture 

 of these materials is used * for road-metal) become 

 stained of a deep blue colour, which has been shown 

 V analysis to be due to ferric ferrocyanide. A dis- 

 NO. 2487, VOL. 99] 



cus/ion on this subject appeared in N.^ture in 1904 

 (vol. Ixxi., pp. 83, 126, 176). F. J. Allen. 



Cambridge, June 24. 



A Note on Chaffinches and Cuckoos. 



One day recently I went to look at a chaffinch's 

 nest which I had known of for some time. I had just 

 begun to climb up the hawthorn-tree in which the 

 nest was placed when I heard the "pink, pink" of an 

 alarmed chaffinch, and immediately about five cock 

 chaffinches and more than half a dozen hens and 

 young ones appeared from what seemed to me now here. 

 These chaffinches flew all round the tree in a most 

 agitated manner, and one cock actually got on top of 

 my head and pulled my hair vigorously, while a hen, 

 which appeared with the other chaffinches, and I think 

 was the mate of my assailant, flew on to the nest and 

 {>ecked at me every time I tried to touch it. Their 

 attack induced me to get down ; and not until I was 

 more than fifty paces from the tree did the other 

 chaffinches go away. 



Not very lone after this I was in the garden when 

 I saw two cuckoos which were flying very low, and 

 I could clearlv perceive that one of them was carrying 

 an e.^^ in its beak, while the other was crying 

 "cuckoo, cuckoo." I know that there has been much 

 dispute as to whether cuckoos do or do not carry their 

 eggs ; but in this instance I can personally testify that 

 a cuckoo was carrying what was obviously an egg. 

 Honor M. M. Perrycoste. 



Higher Shute Cottage, Polperro, Cornwall, 

 June 14. 



Jupiter's Satellites and the Velocity of Light. 



I SHOULD be grateful to any readers of Nature who 

 can find time to send me two postcards, one -cia 

 Siberia and the other via U.S. America, telling me 

 what is the most trustworthy interval of time between 

 the eclipses of Jupiter's first satellite (sidereal revolu- 

 tion id. iSh. 28m.) when the earth and that planet are 

 in conjunction and in opposition. Watson, on p. 503 

 of "A Text-book of Physics," fourth edition, gives 

 T— T' = i992 sec, and Everett, on p. 82 of "C.G.S. 

 System of L'nits," gives as the best determination of 

 the mean distance of the earth from the sun 

 1-49465(10)" cm. If these figures are to be trusted, 

 Romer's method of determining the velocity of light 

 ranks second to none, as it yields the figure 300i2(io)^* 

 cm. per sec. A. W. Warrington. 



Chengtu Fu, W. China, March 3. 



Arcs of Halos. 



The phenomenon described by Dr. Ellison (Nature, 

 June 14, p. 312) is clearly the upper contact arc of the 

 4(5° halo, and is not very uncommon, even in the 

 absence of the halo itself. 



The Meteorological Office "Observer's Handbook" 

 states : — 



"The arcs of upper contact appear with their convex 

 sides turned towards the sun. . . . The colour effects 

 are often brilliant, red being turned towards the sun, 

 i.e. on the convex edge of the halo. The coloration of 

 the arc of upper contact of the halo of 46° is frequently 

 exceedingly brilliant." 



Meteorological memories are proverbially short, and 

 town-dwellers miss many optical phenomena too 

 common in the country to excite comment. 



Walter W. Bryant. 



Royal Observatory, Greenwich, June 26. 



