NA TURE 



[December 9, 1922 



Research Items. 



Surveys in Spitsbergen. — In the Geographical 

 Journal for November -Mr. R. A. Frazer gives an 

 account of some work which he did on the edge of 

 New Friesland in company with Mr. N. E. Odell and 

 Dr. T. G. Longstaff in August 192 1. The party 

 travelled north-eastward for about 25 miles from the 

 head of Klaas Billen Bay into the highland ice of 

 the interior. Crossing the watershed between the 

 western and eastern drainage areas, they surveyed 

 the salient features in a small area lying between 

 the Mount Svanberg group to the south and the 

 peaks around Mount Chernichev to the north. Weather 

 and travelling conditions were bad, and time was 

 short, but the work which was accomplished fills one 

 of the gaps in the skeleton survey of the Russian 

 Arc of Meridian Expedition of 1898-1902. 



Desiccation in the Lake Chad Region. — In an 

 article in the Geographical Journal for November on 

 the Lake Chad region, Mr. F. W. H. Migeod returns 

 to the much debated question of desiccation on the 

 southern edge of the Sahara. According to Mr. 

 Migeod there is abundant evidence of the advance 

 of arid conditions southward into the belt of fertility 

 in Bornu. The dry area has been steadily increasing 

 at a great rate for at least three-quarters of a century, 

 and apparently at a slower rate for many centuries. 

 Mr Migeod cites evidence from the drying up of 

 rivers and ponds, but on the other hand he found no 

 personal evidence of the exhaustion of wells in the 

 part of Bornu which he visited. The evidence from 

 changes in forest growth he does not find conclusive, 

 but with regard to human migration, he points to the 

 significant fact that every successive capital of the 

 Bornu empire during the last six centuries has been 

 south of its predecessor. The general trend of 

 migration is southward, and whenever a new village 

 is founded it is always in a position south of the 

 previous site. 



Problems of Mendelian Ratios. — Mr. R. A. 

 Fisher gives an elaborate mathematical treatment 

 (Proc. Roy. Soc. Edin. vol. 42, Part 3) of certain 

 problems connected with Mendelian ratios. He 

 concludes that the ratio of frequency of the various 

 types in a Mendelian population will be stable only 

 when selection favours the heterozygote, such factors 

 only tending to accumulate in the stock, while other 

 factors will tend to be eliminated. He also develops 

 formula? for determining the rate of mutation which 

 is necessary to maintain the variability of a species 

 under different conditions. We are not competent 

 to discuss his mathematics, but some of his biological 

 statements are perhaps open to criticism. For example, 

 he assumes that recessive factors tend to be harmful or 

 harmful factors recessive, whereas in man the majority 

 of harmful factors are dominant. He also repeats 

 the current fiction that the mutations of (Enothera 

 are explained by the crossing-over of balanced 

 lethal factors. 



Absorption of Water by Root and Stem Tips. — 

 Prof. Priestley and his students have now published 

 the fourth in their series of studies on the anatomy 

 and physiology of the endodermis and related struc- 

 tures in plants. The present contribution (New 

 Phytologist, vol. 21, No. 4) considers the water 

 relations in the growing root and stem tip. Experi- 

 ments of de Vries in forcing water into roots were 

 confirmed and extended, showing that the endodermis 

 prevents leakage of water from the stele into the 

 cortex. At the same time the meristematic root tip 

 before the endodermis is organised was shown to be 



NO. 2771, VOL. I IO] 



impervious to water under ordinary pressures. This 

 is apparently owing to the peculiar non-cellulose 

 composition of the cell walls in this region, in contrast 

 to the corresponding region of the stem tip. The 

 impervious character of this region accounts for the 

 failure of water-leakage from root tips, and is contrary 

 to the views of a French worker who believes that 

 the root tip below the root-hair zone is an absorptive 

 region. 



Coal in South Africa. — Memoir No. 19 of the 

 Geological Survey of the Union of South Africa, 

 issued recently, forms the first volume of a study of 

 the coal resources of the Union of South Africa 

 compiled by Mr. W. J. Wybergh. The coalfields 

 dealt with are those of Witbank, Springs, Heidelberg, 

 and the coalfields of the Orange Free State ; they 

 are all described in considerable detail, numerous 

 analyses are given, and the general character and 

 properties of the coals are fully discussed. It may 

 be of interest to reproduce the author's estimate of 

 the existing coal resources of the Union, although, as 

 he points out, considerable deductions may have to 

 be made from these figures for losses in working. 



fairly 



Witbank Coalfield 

 Springs area 

 Nigel area . 

 Vischkuil-Delmas 



proved 

 Vischkuil - Delma; 



jectural 

 Heidelberg South Rand area 



do. other areas 

 Orange Free State above 



Total .... 



area con- 



7,926,206,000 tons 



485,000,000 ,, 



65,000,000 „ 



218,400,000 ,, 



1,411,200,000 ,, 



8,064,000,000 ,, 



965,544,000 ,, 

 100,000,000,000 



119,135,350,000 tons 



The New Braun Tube. — Two years ago .Mr. J. B. 

 Johnson of the Research Laboratories of the Western 

 Electrical Co., and the American Telephone and 

 Telegraph Co., exhibited to the American Physical 

 Society a Braun cathode ray tube operating at low 

 voltage, and an abstract of a more complete descrip- 

 tion of the tube in its present improved form will be 

 found in the September issue of the Journal of the 

 Optical Society of America and Review of Scientific 

 Instruments. The cathode consists of a strip of 

 platinum covered with an oxide, the anode of a tube 

 of platinum 1 cm. long and o-i cm. diameter, only 

 o-i cm. from the tip of the cathode. Between 

 cathode and anode is a metal shield with a small hole 

 in it through which the electrons from the cathode 

 pass. Beyond the anode are the two pairs of de- 

 flector plates at right angles to each other, which can 

 be connected to the two sources of electromotive 

 force which are to be compared. The electrons 

 finally impinge on a fluorescent screen and their 

 deflection is of the order o-i cm. per volt applied to 

 the deflector plates. When the plates are replaced 

 by coils, the same deflection is obtained per ampere 

 turn in the coils. In the paper referred to, the 

 hysteresis loop for iron in an alternating field and the 

 characteristic curve for an oscillating valve tube are 

 given. At the exhibition of the tube before the 

 Institution of Electrical Engineers on November 16, 

 the anode current and grid voltage curve of a valve 

 was shown. As the cathode ray has to produce 

 ionisation as it moves sideways, it is not possible to 

 obtain a sharp spot at frequencies of more than 

 10 6 per second, but below that figure the slight 

 pressure of mercury vapour in the tube ensures a 

 sharp image. With the oxide cathode an electro- 

 motive force of 300 volts is sufficient to run the tube. 



