July 28, 1923] 



NA TURE 



145 



patterns of the secondary layers may differ from 

 each other and from that of the primary wall 

 upon which they are deposited. This difference in 

 point of view should promote the advance of our 

 knowledge of the wall structure, and certainly both 

 these workers have materially added to our technique 

 in this difficult field. One may cite, for example, the 

 photographic illustration in the present paper of the 

 growth-rings first demonstrated by Dr. Balls and 

 of other wall structures, such as pits and spirals. 

 Mr. Denham illustrates and discusses at some length 

 the various abnormalities in cell-wall structure met 

 with by several workers, and shows that considerable 

 importance may attach in this connexion to the 

 development of the hairs crowded and compressed 

 within the boll. Based partly upon the study of the 

 staminal hair of Tradescantia, the very interesting 

 suggestion is made that the spiral striation in the 

 cell wall may follow from its deposition along the 

 track of the spirally rotating cytoplasm. Such a 

 spirally rotating band of cytoplasm will of necessity 

 travel in two streams, lying side by side but moving 

 in opposite directions, and the deposition of particles 

 from such a moving band would be expected to 

 vary from the centre of the band to the margin. 

 Here the author finds a possible explanation of the 

 double spiral line of weakness which he demonstrates 

 in the wall of the hair and regards as the cause of 

 the convolutions which are so important to the 

 spinner. 



The Diamond-pipes of Arkansas. — The first 

 diamonds from Arkansas were picked up near Mur- 

 freesboro in 1906, on the surface of a pipe of peridotite 

 that had been correctly appreciated by J. C. Branner 

 seventeen years before. Abundant small stones are 

 now extracted from surface-diggings in the decom- 

 posed peridotite or peridotite-tufif that fills exploded 

 vents, and the associated strata clearly show that the 

 intrusions occurred at the opening of Upper Cretaceous 

 times. The question as to whether the diamonds 

 were generated in the ultrabasic magma, or whether 

 they have been brought up from some mass through 

 which the invader broke, cannot be regarded as 

 settled ; but the list of their associates, including 

 garnet and diopside, seems to indicate the presence 

 of eclogitic rocks in the depths. The occurrences have 

 now been described by H. D. Miser and C. S. Ross in 

 Bulletin 735-I of the U.S. Geological Survey (1923). 

 The largest diamond so far recorded from Arkansas 

 weighs 20-25 carats, which comes within the limits 

 of what may be regarded as a large stone. The age 

 of the pipes is of interest in connexion with what is 

 now known as to the S. African examples. 



The Carboniferous Feora of Great Britain. — 

 Under the auspices of the Geological Survey, Dr. 

 Robert Kidston is bringing together the results of his 

 long and happily continuing work on British Carbon- 

 iferous plants. It is proposed to issue some ten 

 quarto parts as Volume II. of the palaeontological 

 memoirs of the Survey, including critical descriptions 

 and illustrations of every known species in the flora. 

 The first two of these parts are now ready (1923), 

 price 15s. and 12s. (yd. respectively. There is nothing 

 on the covers to indicate to the purchaser that he is 

 not receiving the whole work on the " Fossil Plants 

 of the Carboniferous Rocks of Great Britain " in the 

 limits of one part, and the separate sheet issued with 

 Part 2 would lead him to conclude that he was 

 dealing with the second part of the second volume of 

 the book. The final title-page will set this right for 

 our librarians. So far, all the species retained in the 

 " form genus " Sphenopteris have been dealt with ; 

 but it is suggested that some may in the future be 



NO. 2804, VOL. 112] 



removed from the ferns to the pteridosperms as their 

 mode of fructification becomes known. The photo- 

 graphic plates, by the Zinc Collotype Co. of Edin- 

 burgh, are admirable in the lighting of the specimens. 

 Dr. Kidston's broad outlook makes the memoir a 

 noble contribution, not only to palaeontology, but to 

 stratigraphy. On the latter point we may note that 

 the author adopts " Westphalian, " but not " Visean," 

 " Tournaisian," or our own broad " Aronian," and 

 that the " Millstone Grit " horizons become divided 

 (p. 14) between a " Lanarkian " series in the Upper 

 Carboniferous and the highest beds of the Limestone 

 series in the Lower Carboniferous sub-system. 



The Salts of the Dead Sea and River Jordan. 

 — In the Geographical Journal for June Mr. W. Irwin 

 has a paper on this subject. Analyses of samples of 

 Dead Sea water show considerable variation according 

 to the spot from which the sample is taken, but the 

 total solids do not vary greatly. The outstanding 

 change is a decrease of sodium salts and an increase 

 of magnesium salts on passing from the north to the 

 south, and to the deepest part of the centre of the 

 lake. This alteration can be caused only by the 

 sodium salts crystallising out on the bottom, leaving 

 the more soluble magnesium salts in solution. Tests 

 of Jordan water show a surprising salinity, averaging, 

 at Jericho, 0-0364 gm. chlorins per 100 c.c. Further 

 analyses in different stretches of the river gave 

 interesting results. As near its source as the Waters 

 of Merom it is highly impregnated with salts, chiefly 

 chlorides of sodium and magnesium, and the com- 

 position of the water does not change as far as the 

 Sea of Galilee. In the Sea of Galilee there is a slight 

 increase in these chlorides and a decrease in calcium 

 sulphate and silica, due no doubt to evaporation on 

 one hand and precipitation on the other. By the 

 time the river reaches Jericho there is an increase of 

 salts, especially magnesium chloride. The result of 

 these investigations is to suggest that the principal 

 origin of the salt in the Dead Sea is from the 

 Jordan, which brings it from Hermon and possibly 

 Lebanon. Assuming the bulk of magnesium chloride 

 to be provided by the Jordan, the present level of 

 the Dead Sea must be rising at the rate of i ft. in 

 125 years, for the Jordan brings in 181 million pounds 

 a year, and if the solution is already concentrated and 

 none crystallises out, as appears to be the case, an 

 annual additional depth of water estimated to be 

 1/125 ft. is required. 



West Indian Earthquakes. — Prof. S. Taber has 

 recently published an interesting study of the seismic 

 belt in the Greater Antilles (Bull. Seis. Soc. America, 

 vol. 12, 1922, pp. 199-219). In this region, the 

 major relief features are zones of normal faulting 

 developed in late geological times, and still, as the 

 occurrence of earthquakes shows, being developed. 

 The two most persistent fault-zones are the Swan 

 Island- Jamaica-South Haiti and the Cayman Islands- 

 Sierra Maestra - North Haiti, which are roughly 

 parallel for a distance of nearly 2000 km. and are 

 only 100 to 150 km. apart. The narrow strip 

 between these fault-zones is depressed in its western 

 and central portions so as to form the Bartlett trough 

 (3506 fathoms). With few exceptions, all strong 

 Antillean earthquakes have originated along a few 

 well-defined belts which coincide with the major 

 fault-zones of the region. There is no evidence 

 either of a continuous change in the seismicity of 

 the region or of any well-defined periodic variation. 

 When severe earthquakes have been separated by 

 a short time-interval, their epicentres have been in 

 the same fault-zone and only a short distance apart, 

 thus indicating that the displacement was being 



