April 8, 1909J 



NA TURE 



^19 



directions of vibration in the adjoining crystal sections 

 wliich make the smaller angle with each other, so that 

 the Becke effect is mainly due to the relation between their 

 indices of refraction. The author discusses in detail the 

 effect of the refractive indices of the different directions of 

 vibriition on the result. 



Geological Society, March 24. — Prof. W. J. Solla?, 

 F.R..S., president, in the chair. — Glacial erosion in North 

 Wales : Prof. W. M. Davis. An excursion around 

 Snowdon in 1907, followed by another in 1908, led the 

 author to think that a large-featured, full-bodied moun- 

 tain of pre-Glacial time had been converted by glacial 

 erosion during the Glacial period into the sharp-featured, 

 narrow-spurred mountain of to-day. The indifference of 

 topographic form to the trend of formation boundaries and 

 the insequent stream arrangement are what might be ex- 

 pected as the result of prolonged erosion upon a mass of 

 complicated and resistant structure. The author is of 

 opinion that the upland deserves classification rather with 

 peneplains ; he suggests for it a Tertiary date, and argues 

 th.it Snowdon had a relief of some 2000 feet above the 

 plain. It is considered that the dissection of North Wales 

 must have been less developed in pre-Glacial times than 

 in Devon to-day. On this assumption it is possible to 

 make a tentative restoration of the pre-Glacial form of 

 Snowdon. The chief abnormal features of Snowdon are 

 thi' following : — Alongside the summit and slopes of a 

 •• mod " stand the head-cliffs of a rock-walled cwm, in 

 the floor of which talus is accumulating. The cwm-floors 

 are generally stepped, and the streams cascade down into 

 the valleys. The slope of the main valleys occasionally 

 decreases even to the point of reversal, as where lakes 

 occur, and in the immediate neighbourhood of smoothly 

 graded, waste-covered slopes, knobby or craggy ledges and 

 bars of rock often appear. Two out of four possible hypo- 

 theses put forward are discussed — " that glaciers are 

 essentially protective agencies " or that they " are active 

 destructive agencies." It is found that certain facts, and 

 especially those relating to rock-steps, cannot be explained 

 on the protection theory, while the theory of a destructive 

 agency seems to explain most of the facts. There is no 

 systematic relationship between the height of the cwm- 

 ciiffs and the distance of the front rock-step; the serration 

 of " cribs " or arites cannot be explained by pre-Glacial 

 or post-Glacial weathering, according to the protection 

 theory. No consistent explanation of the valley-steps can 

 be found under the theory of ice protection, whereas they 

 are explicable on the assumption of glacial erosion. The 

 catenary curve of the cross-section of such valleys as those 

 containing Llyn Gwynant and Llyn Cwellin might be 

 expected to result from long-continued ice erosion, and 

 the occurrence of great cliffs on the sides of these valleys 

 is not inconsistent with such an origin. The most striking 

 ease of a glacial overflow is that at the head of the 

 Nantlle valley, which appears to have carried much of the 

 west Snowdon ice. The head of the pass would seem to 

 have been farther westward and higher in pre-Glacial 

 times. 



Dublin. 

 Royal Dublin S'^cietv, .March 2V — Prof. A. F. Dixon 

 in the chair. — Black scab or potato-wart (Chrysophlyctis 

 ci'dobiotica, .Schilb.), and other Chytridiacefe : Prof. T. 

 Johnson, The author gave an illustrated account of the 

 origin, structure, and conditions of germination of the 

 nuiUisporous resting sporangia of the parasitic fungus 

 Chrysophlyctis endobiotica, Schilb., the cause of black scab 

 or black wart in potatoes. The successful germination of 

 the " resting spores " was announced in a letter to N.\ture" 

 in November, 1908. The author, basing his observations 

 on the examination of type-material from M. Trabut, com- 

 pared beet-tumour, due to Urophlyctis or Cladochytrium 

 Icproidcs, with potato-wart, and showed how they differ. 

 He also discussed Magnus's views on the genus 

 Urophlyctis, and stated that flax yellowing caused by 

 Astciocystis radicis, de Wild., not uncommon in Ireland 

 a few years ago, is now kept in check by potash manuring. 

 Eiiryrliasina Dicksonii (Wright), Magnus, and Olpidium 

 spliiiccllnnitii, Kny, two Irish marine Chytridiacete, the 

 latter being hitherto unrecorded for Ireland, were described. 



NO. 2058, VOL. 80] 



— The Scandinavian origin of the hornless cattle of the 

 British Isles : Prof. James Wilson, The common opinion 

 is that the British hornless breeds of cattle originate; 

 cither as reversions to an older hornless type or as spon- 

 taneous variations, as Darwin believed, from the horned 

 to the hornless condition. Both these theories are wrong, 

 for these reasons : — (o) the self-same variation occurred in 

 too many places — twelve or fifteen at least — in Britain ; 

 ((>) it ought to have occurred as frequently among similar 

 cattle elsewhere, in the Low Countries, for instance ; and 

 (f) it has ceased to occur v/ithin what might be called 

 bovine historic time. The first suggestion that the British 

 hornless cattle are of Scandinavian origin comes from the 

 localities in which they were found in the eighteenth 

 century. These were what might be called pockets round 

 the coasts of Britain and in Ireland, viz. Suffolk, Holder- 

 ness, Forfarshire, Aberdeenshire, Morayshire, Sutherland, 

 Skye, Galloway, Somerset, Devon, and the north and 

 west of Ireland. Besides being hornless, these coast cattle 

 agreed in several other characteristics — they were light 

 dun in colour, or bore colours derived from light dun ; 

 they were small, narrow chined, short legged, sickle- 

 hocked, and good dairy cattle. They arrived in Britain 

 before 1066, and not before the end of the Anglo-Saxon 

 invasion. Cattle of the same kind were found in other 

 Norse settlements, viz. Normandy, the Channel Islands, 

 north Holland, Orkney, Shetland, and Iceland, and cattle 

 of the same kind are still to be found from Norway to 

 north Russia. In all probability they are descended from 

 the cattle of the Scythians, referred to by Herodotus, and 

 may be traced back either to Egypt or western Asia. — 

 The osmotic pressures of the blood and eggs of birds : 

 W. R. G. Atkins. The blood of Callus bankiva, 

 Meleagris gallopavo, .'\nas, Anser, and Phca americana 

 was examined, and the freezing point of the blood of 

 each species was found to be almost constant, the varia- 

 tions being of the same order as those met with in 

 mammals. The eggs of Gallus and Anas were studied ; 

 thev are not isotonic with the blood, freezing at — o°-45 C, 

 while the blood freezes at — o°-6i C. and — o°-57 C. re- 

 spectively. This difference in the freezing point is more 

 than accounted for by the diminution in inorganic salts 

 in the egg as compared with the blood. 



P.'lRIS. 



Academy of Sciences, March 29. — M. Bcuchard in the 

 chair. — Complement and summary of the observations 

 made at Meudon Observatory on Morehouse's comet : H. 

 Deslandres, A. Bernard, and J. Bosier. After 

 summarising the work which has been done on this 

 comet, the following are mentioned as noteworthy 

 points : — the presence of three new lines or bands {\\ 456, 

 426, and 401) of unknown origin, noticed for the first 

 time in the tail of Daniel's comet; the presence of only 

 one group of cyanogen bands ; and the presence of a 

 characteristic nitrogen band. — The diffraction of Hertzian 

 waves : H. Poincare. A mathematical investigation 

 which throws light on the striking effects of diffraction 

 obtained in wireless telegraphy over great distances. — 

 Some extremely simple formulae relating to the coefficient 

 of self-induction and to the time constant of a very long 

 bobbin : Marcel Deprez. The formula given for the 

 coefficient of self-induction is Uja, in which L is the 

 total length of wire wound on the bobbin, and a the 

 length of the bobbin. — Concerning Trypanosoma pecaitdi, 

 T. "dimorphon, and T. congolense : A. Laveran. Two 

 sheep inoculated with Tr. pecaudi became infected ; at 

 the end of six months they were cured, and were com- 

 pletely immune against this organism. Inoculated then 

 with T. dimorphoti, thev were infected like new animals. 

 One of these, after cure, 'had not acquired immunity against 

 T. dimorphoii, but the other proved to be immune. The 

 latter animal, then inoculated with T. congolense, contracted 

 the infection. All these observations confirm the original 

 view that these three trypanosomes belong to entirely, inde- 

 pendent species.— M. Boudier was elected a correspondant in 

 tlie section of botanv in the place of the late M. Masters.— 

 Certain cyclic systems : G. Tzitieica.— A general prin- 

 ciple of uniformisation : Paul Koebe.— An arrangement 

 for measuring very small displacements of the lines of 



