164 



NA TURE 



\_Dec. 13, 1883 



Lord Rayleigh's problem.' He showed that, in a certain case 

 in which the analytical solution leads to an infinite value, there 

 are waves in the continuous streams in diametrically opposite 

 phases, and that the vortical stratum consists of a series of oval 

 vortices. The uniform current flouing over existing ripple-mark 

 exhibits almo>t a realisation of this mode of motion, one of the 

 streams of fluid bein^j replaced by the sandy undulations. The 

 same lond of motion must exist in air when a gust of wind blows 

 a shallow puddle into standing ripples. 



It seems probable that what is called a mackerel sky is an 

 evidence of a mode of motion also closely similar to that de- 

 scribed by Sir William Thomson. M. de Candolle's suggestion 

 that cirrus is aerial ripple-mark may then be regarded as sub- 

 stantially correct. 



If two horizontal currents of fluid exist one above the other, 

 the liyer of transition from one to the other is dynamically un- 

 stable, but it is probable that if a series of vortices be inter- 

 pohled, so as to form friction rollers as it were, it becomes 

 stable. It is likely that in air a mode of motion would be set 

 up by friction, which in frictionless fluid would be stable. 



The formation of clouds is probably due to the saturation with 

 moisture of one current and the coldness of the other. 



The direction of striation and velocity of translation of 

 mackerel clouds require consideration according to this 

 theory. 



It appeirs that if a mackerel sky be formed beween two 

 aerial currents, the striations are parallel to that direction in 

 which the two currents have equal component velocities, and the 

 component velocity of the clouds parallel to the striations is 

 equal to the component velocity of either current in the same 

 direction. 



The resultant velocity of the clouds is equal to a half of the 

 resultant velocity of the two currents and the component velo- 

 city of the striations perpendicular to themselves is the mean of 

 the components of velocity of the two currents in the same 

 direction. 



The account which is given in this paper of the formation of 

 ripple-marks shows it to be due to a conplex arrangement of 

 vortices. The difficulty of o'lservation is considerable, and 

 perhaps some of the conclusions arrived at may require modifi- 

 cation. It is to be hoped that other etperimenters may be 

 induced to examine the question. 



The reader is referred t) the origi lal for the fij^ures, which 

 are necessary to an adequate explanati )n of the phenomena and 

 conclusions. 



NOTE ON DEAFNESS IN WHITE CATS' 

 'T'HIS curious occurrence has lon^ been a matter of interest to 

 me, originally because ca's have ahv-ays been very favourite 

 pets in my household, and still more because the occurrence 

 am m^st them of deafness was used by Mr. Darwin in his first 

 edition of "Animals and Plants under Domestication" as an 

 illustration of correlated variability. He was under the impres- 

 sion that white cats with blue eye; were invari.ably deaf. 



I had collected a number of observations which I had person- 

 ally made, and I found ihat some white cats « ere deaf which had 

 the ordinary yellow eyes, and that some white cats with blue 

 eyes could hear perfectly well. 5 have never heard of deafness 

 in any but a white cat, and all the deaf uhite cats I had per- 

 sonally examined were males. Therefore, in N.iture, 1873, 

 I published a brief note pointing out Mr. Darv\in's error. In 

 his second edition .Mr. Tlarwin established two cases of deafne-s 

 m female white cats, so that the conclusions of b^th of us were 

 upse-, and this wholesale destruction of theories has been com- 

 piled by the birth in one of my feline families of a white 

 kitten, fem.ale, with perfectly yell nv eyes, and absolutely deaf. 

 She lived with us for two years, and her mi-fortune was quite 

 permanent. My conclusions from the facts observed by myself 

 now may he formulated in this «ay, that congenital deafness is 

 not known to occur in any animal bnt the cat, though I am not 

 quite sure but that one white mouse I had some years ago was 

 deaf, and that no cats but those entirely white are ever deaf. As 

 female cats are far more common than males (and this seems 

 to be true of white cats as well ar. those of other c ilour.-), and 

 as I have known only one deaf female cat for some twenty 

 deaf males, I think I may assume that deafness is more com- 

 mon among males than among females. The colour of the 



I u^Vu",' ~°r"i,''" ."','880, pp. 45-(S, and see correction on p. 70. 

 Head before the Birmingham Philosophical Society, October 1 r 



eyes has evidently nothing to do with the deafness, though it has 

 with the colour of the fur, and .>^eems to be dependent on the 

 sime process — an arrest of development. The eyes of nearly all 

 kittens are blue for some weeks after birth, and the sime cause 

 which arrests the pigmentation of the fur arrests in a very 

 much smaller number the pigmentary growth in the eye. I 

 have been told of two cases of complete absence of pigment 

 in the eyes of two cats (albinism) as is seen so commonly in 

 rabbits, guinea-pigs, rats, and mice, but I have not been able 

 properly to authenticate them. These cats were said to be not 

 deif. 



In 1872 I obtained a cat from Hertfordshire as an example of 

 the polydactilism which is very common there, and when he 

 arrived I found that he was white, that he had one eye a bright 

 blue and the other a bri.;ht yellow, and that he v\as profoundly 

 deaf. He was by far the most interesting cat I have ever 

 possessed, and must be well remembered by many members of 

 this Society ^ho have favoured my h.iu e with their presence as 

 "Old Pud;.(e," poseised of all the feline virtues, and many of a 

 more human ty|)e — and free from vice of every kind. He lived 

 with 'us for eleven years, and died last winter of peritonitis. 

 Whilst living with us we made many observations concerning 

 his deafness, and I easily determined that it was purely tympanic 

 — that is, he was deaf to impressions conveyed through the air, 

 but his inte'liience could be reached by impressions conveyed 

 through solid media. When I wanted him to come to me I gave 

 a peculiar --harp stamp on theflojr, and he immediately responded 

 to the signal, even if be was on a chair or table. It is very 

 remarkable that this ccmgenital deafness is in no way associated 

 in the cat with mutism. Human deaf-mutes generally are those 

 in whom deafness is cochlear as well as tympanic, and the result 

 of such disease as scarlet fever in very early life. One other 

 peculiarity he had is that for about fouryeirs he suffered from 

 occasional lits of epilepsy of a very severe kind. They came on 

 always durinij his sleep, and for their fir^t indication had the 

 painful peculiarity that the cat seized the tip of his tail and bit 

 it off, and in this way his tail was shortened considerably. 

 Every kind of white animal I have kept as a pet has been the 

 subject of epilepsy, and the association is suggestive when we are 

 told, as I have been frequently, that the disease is unknown 

 amongst negroes. 



I sent the body of my old cat to Prof. Flower for the purpose 

 of having an inve-tigation made into the cause of his deafness. 

 Prof. Flower had a most careful investigation of the cinditi3n of 

 his ears made by two mo^t competent investijalors — Dr. Cum- 

 berbatch and Dr. Heneage Gibbs. The result, briefly stated, is 

 that all the structures in the ears were mrmal save the tympanic 

 membranes, in which there were triangular gaps extendmg from 

 the roof to just below the centre, the bases of the gaps being 

 directed upwards, and their anterior side being formed by the 

 handles of the mallei. The gaps appeared to be congenital, and 

 were quite symmetrical ; all the other apparatus of the ears was 

 normal, and the audito-y nerves were of normal size and 

 structure. 



The only congenital defect kmwn in the human tympanum 

 is a very minute aperture, of rare occurrence, and due to the 

 patency of the fissure of Kivinus. The tympanic deficiency in 

 the white cat seems to be in no way associated with this form of 

 arrest. 



The re-ults of the observation are interesting, though the 

 subject may perhaps be regarded as trivial, as by it the point 

 raised by Mr. D.arwin is finally established. It really is a case, 

 and a very well marked one, of correlated variability, and its 

 great interest is that the three .structures affected — the fur, the 

 iris, and the tympanic membrane — have a common origin from 

 the epiblast. Had the defects observed in this cat been cochlear, 

 the difficulty of understanding them would have been very great, 

 as the structures of the internal ear arise from the mesoblast, 

 according to Balfour. Lawson Tait 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 

 Cambridge. — The recent recommendations of the General 

 Board of Studies have .all been passed. These include the 

 appointment of a Professor of Pathology next term, of Readers 

 in several subjects, including Comparative Philology and Botany, 

 of University Lecturers in connection with Special Boards, in- 

 cluding Medicine (four). Mathematics (five), Bi dogy and Geo- 

 logy (six). History and Archeology (five). Moral Science (one). 



