262 



NA TURE 



[August 19, 1922 



species ; three species, of which two are new, of 

 Sauvagesia ; and a new species of Durania complete 

 the series. Among the associated fossils cited is 

 Balanocrinus mexicanus, n.sp., which forms the sub- 

 ject of a separate paper by F. Springer (torn, cit., 

 art. 5). This is the first known occurrence of the 

 genus in America. 



The Flotation of Continents. — M. E. Gagnebin, 

 of the University of Lausanne, has provided a masterly 

 review of Wegener's hypothesis of the movement of 

 continental masses over the general surface of the 

 globe. In ten pages of the Revue generate des Sciences 

 naturelles, vol. xxiii. p. 293, 1922, he states the main 

 features of the argument, discusses the problems 

 raised, and furnishes references and footnotes that 

 make his lucid essay an almost essential introduction 

 to Wegener's " Entstehung der Continente " (see 

 Nature, vol. 109, pp. 202 and 757). It is interesting 

 to notice that the relations of folded zones to those 

 of subsidence on the earth is one of the subjects 

 discussed at the International Geological Congress in 

 Brussels in August 1922. 



The Matrix of Diamond. — The question of 

 whether diamond separates out from ultrabasic 

 igneous magmas, or is carried up in these exceptional 

 magmas because they have traversed deep-seated 

 metamorphic rocks, is once more raised by the 

 description of the diamond-bearing gravels of the 

 Somabula Forest in Southern Rhodesia (A. M. 

 MacGregor, Geol. Surv. S. Rhodesia, Bull 3, 1921). 

 These fluriatile beds form part of the Karroo systems, 

 and the kimberlite pipes of S. Africa are of later date. 

 The author suggests that the diamonds were washed 

 from a kimberlite of unusually early age, since he 

 favours the view of their igneous origin. New interest 

 is given to the kimberlite pipes of Africa by H. S. 

 Harger's discovery (Trans. Geol. Soc, S. Africa, vol. 

 xxiv. p. 1, 1922) that an example in the Riversdale 

 district of the Cape Province cuts strata of Uitenhage 

 (Cretaceous) age. 



Critical Research on Fossil Brachiopoda. — 

 The transference of well-known species to new genera 

 as investigation becomes more precise often leaves 

 little to be said for an original genus the name of 

 which has become known throughout the world. 

 This is sadly the case with Rhynchonella, to which 

 Mr. S. S. Buckman (Mem. Geol. Surv. India, Palae- 

 ontologia Indica, New Ser., vol. 3, Mem. 2, " The 

 Brachiopoda of the Namyan Beds, Northern Shan 

 States, Burma ") now assigns only two species, 

 R. loxia Fischer of the Portlandian, and R. variabilis 

 Davidson of the Kimmeridgian (p. 57). The author 

 quotes (p. 91) his previous conclusion that no Meso- 

 zoic species can be assigned to Terebratula Miiller, 

 1776. On pp. 8 to 11 he describes his method of 

 " burning " specimens of fossil brachiopods ; when 

 the shell is heated and dropped into water, it commonly 

 flakes off from the internal cast, and the characteristic 

 muscular scars are clearly traceable on the mould. 

 Much, of course, depends on the infilling material, 

 and oolitic limestone yields poor results. The'method 

 has been elaborated by Mr. Buckman from an observa- 

 tion by Mr. T. H. D. La Touche (p. 2), who noticed 

 that the fossils fell out easily from material that had 

 passed through Burmese lime-kilns, and who pro- 

 ceeded to treat his rocks in a big fire " with very 

 satisfactory results." 



Evolution of the Graptolites. — The numerous 

 geologists who wish to keep abreast of progress in the 

 classification of Older Pakrozoic strata will find much 

 guidance in a paper by Dr. Gertrude Elles on " The 

 Graptolitic Faunas of the British Isles " (Proc. Geol. 

 Assoc, vol. 33, part 3, 1922 ; price 5s.). Since it seems 



NO. 2755, VOL. I IO] 



uncertain if hydrozoan, or even cnelenterate, affinities 

 can be maintained for graptolites and their allies, a 

 separate class of organisms, the Graptolithina, has 

 been established, subdivided into two orders, the 

 rapidly changing Graptoloidea and the almost 

 stationary Dendroidea. In the same prudent spirit 

 the term rhabdosome replaces polypary, and theca 

 hydrotheca. The virgula of older descriptions of 

 graptolites disappears. Attention is well directed to 

 the nema, the hollow thread-like prolongation of the 

 apical portion of the sicula, as being the organ of 

 attachment essential to the welfare of the rhabdosome. 

 In the earlier pendent graptolites the nema is un- 

 protected ; but in forms regarded as scandent, such 

 as Diplograptus, and also in some uniserial genera, it 

 is protected, and is sometimes wrapped round the 

 bases of the thecae. Many of the points mentioned 

 are quoted from work published by the author 

 and other investigators, and recognised by modern 

 writers, such as A. M. Davies ; but the present 

 summary, the clear diagrams of types successively 

 evolved, and the stratigraphical table, render this 

 paper by Dr. Elles valuable in all colleges as a sup- 

 plement to established text-books of palaeontology. 



Vertical Circulation in the Atlantic. — A. 

 Merz and G. Wiist (Zeitschrift der Gesellschaft fur 

 Erdkunde, Berlin, 1922, No. 1-2) discuss the nature 

 and causes of the vertical circulation of the water 

 of the Atlantic Ocean, reviewing the various descrip- 

 tions and explanations so far published. It has 

 been known, in a general way, that water which is 

 relatively warm and fresh flows on the surface from 

 the region of equatorial rains and calms north and 

 south to the sub-tropical zones, while water which 

 is relatively cold and dense flows in the opposite 

 directions as under-currents. This system of drifts 

 now appears to be of very limited depth. The 

 superficial warm currents extend to about 50 metres 

 while the under-currents have their main stratum 

 at a depth of 75-150 metres from the surface. The 

 cause is differences of density rather than differences 

 of temperature. 



Dust-Raising Winds. — This subject is dealt with 

 in the Memoirs of the Indian Meteorological De- 

 partment, vol. 22, part 7, by Dr. C. W. B. 

 Normand. Observations were made on dust pheno- 

 mena in Mesopotamia in 1918, and these, together 

 with Dr. Hankin's observations in a preceding memoir, 

 are correlated with those of other observers in other 

 countries. The camp in Mesopotamia was situated 

 at Samarrah, near the edge of the vast low plateau 

 known as Jezireh, where the dust in places lay knee- 

 deep. With even light winds in August and Sep- 

 tember it was no uncommon occurrence to see three 

 or four dust-devils of great height meandering with 

 the breeze on the plain. The base of many of these 

 was only about 5 metres in diameter and the height 

 was at least 300 metres. For the origin of dust- 

 devils a highly unstable vertical distribution of 

 temperature is said to be a necessity. At Samarrah 

 the author attributes the impetus to be often due to 

 the incinerators at the various camps for burning 

 refuse. The " primary " dust-storm in Mesopotamia 

 occurs principally between 4 p.m. and midnight in 

 the months of March, April, May, and September ; 

 they are always associated with cloud, and were 

 often followed by rain, thunder, and a marked fall 

 in air temperature. The dust-storms in spring are 

 almost always associated with thunderstorms and 

 are said to be undoubtedly due to the descending 

 currents which are known to occur in front of thunder- 

 storms. Interesting information is given on the cause 

 of dust-raising by wind, and on turbulence and the 

 density of dust at various heights. 



