July 8, 1922J 



NA TURE 



55 



butterfly Lymantria dispar, the lice Pediculus humauus 

 vars. capitis and corporis, Gammarus and Drosophila, 

 and describes some examples from his own cultures 

 of Daphnia. In Daphnia the intersexes appear not 

 among hybrid examples as in the other cases cited 

 above, but arise during parthenogenetic reproduction, 

 and, on the whole, they seem to have been biassed 

 originally towards the male sex and then to have 

 been secondarily feminised. Dr. Vaulx proceeds to 

 discuss whether the intersexual condition is due to 

 the action of two determining factors acting simultan- 

 eously or to two forces, e.g. hormones, working 

 successively, and remarks that sex appears to depend 

 on numerous factors or elements, and it has hitherto 

 been found possible to investigate only some of 

 these. He considers that the facts examined lead 

 to two inferences : (a) That sex does not depend on 

 discontinuous factors, or the absence or presence of 

 something as chromosome formulas suggest, but on 

 complex causes resulting in continuous variation ; 

 (b) every unisexual individual possesses potentially 

 the attributes of the other sex, and these may be 

 revealed under certain conditions ; it does not seem 

 that one sex can be really homozygous. 



Arctic Rotifera. — In a short account of the 

 Rotifera of the Canadian Arctic Expedition (Report, 

 vol. viii.) Mr. H. K. Harring records 64 species, four 

 of which are new, among which is a pelagic Synchasta 

 —an addition to the extremely small number of 

 rotifers known to exist in the open ocean in waters 

 of normal salinity. The total absence of the genus 

 Brachionus so abundant elsewhere is noteworthy. 



Carbonaceous Material in Oilshale. — Mr. E. 

 H. Cunningham Craig's recent paper on kukkersite, 

 the oilshale of Esthonia (read before the Institute of 

 Petroleum Technologists on May 9), reopens — among 

 other controversial matters — the question of the 

 origin of the carbonaceous material present in oilshale, 

 a problem upon which the study of this particular 

 deposit may be destined to shed considerable light. 

 The shale is of Ordovician age, and forms part of a 

 Lower Palaeozoic sequence remarkable alike for its 

 sedimentary characters and its simplicity of geological 

 structure. Palaeontologically the shale has received 

 recent attention from Mr. H. Bekker, who has not 

 only described the Kukkers stage (C 2 ), but has given 

 some account of the lithology and mode of deposition 

 of the deposit, together with his views on the origin 

 of the bitumenous matter present. His conclusions 

 differ in many respects from those of Mr. Cunningham 

 Craig, the latter regarding the deposit as a relic oil- 

 field, the former stressing the importance of the part 

 played by diatomaceous algae and bacteria under a 

 changing environment. Mr. Cunningham Craig re- 

 gards the shale as being formed by impregnation 

 with inspissated petroleum, derived from the under- 

 lying Cambrian beds, a theory presenting many 

 difficulties, some at least as formidable as those 

 possibly occasioned by the phytoplanctonic theory. 

 Apart from this, the commercial possibilities of the 

 shale are extremely favourable, though one gathers 

 from Mr. Cunningham Craig's remarks that the type 

 of retort used in the past has not been the success 

 anticipated. He estimates the available reserves as 

 1000 million tons. The yield of oil, at present varying 

 from 40 to 50 gallons per ton, could easily be raised 

 to 70 or even 80 gallons per ton, the oil having a 

 specific gravity not higher than 0-93 and containing 

 very little sulphur. Labour is cheap, and the cost of 

 working and refining the shale should not be great. 

 Altogether Esthonia possesses a deposit valuable 

 alike from scientific and economic standpoints, and 

 the progress of development of this shale will be 

 watched with wide interest. 



The Drought of 192 i. — A communication is 

 given in the Quarterly Journal of the Royal Meteoro- 

 logical Society for April by Mr. C. E. P. Brooks and 

 Mr. J. Glasspoole, of the Meteorological Office, on 

 the drought of 192 1, dealt with under the headings of 

 the rainfall of the British Isles and the causes of 

 drought in the British Isles. The year 1921 was in 

 certain areas a year of unprecedentedly small rainfall. 

 The only years since 1850 at all comparable with 

 1921 were 1854, 1864, 1870, and 1887. In 1854 the 

 deficiency of rain reached its maximum in the south- 

 east, where it was more than 30 per cent., to the 

 east of a line roughly from Bournemouth to Lincoln. 

 In 1864 the maximum deficiency exceeded 30 per 

 cent., over large areas along the east coast and in 

 Devon and Herefordshire. In 1870 the greatest 

 deficiency, exceeding 30 per cent., occurred in the 

 central plain of Scotland and locally in the south and 

 centre of England. In 1887 deficiencies of more 

 than 30 per cent, were widespread in the centre of the 

 British Isles, especially in the south-west of Ireland 

 and in a broad band across England from Southport 

 to Hull. For England and Wales, 1921 was the 

 driest year since 1850, while for the British Isles as 

 a whole, only one year, 1887, was slightly drier. 

 Indeed, 1921 was probably the driest year since 1788 

 for England and Wales. A comparison is also made 

 between the general rainfall in 1921 with that of 

 other dry periods of three to nine months' duration, 

 and maps are given showing the several percentages. 

 In the second part of the communication the drought 

 is considered as related to abnormalities in the 

 circulation of the atmosphere. Droughts in the 

 British Isles are closely related to the establishment 

 and the persistence of local anticyclonic conditions, 

 and an attempt is made to find how these abnor- 

 malities are related to others in different parts of the 

 world. Maps of the world showing deviations of 

 pressure from normal during the chief periods of 

 drought in the British Isles are given for the occur- 

 rences since 1864. Generally speaking, low pressure 

 over the polar regions appears to be an essential 

 feature of drought in the British Isles, and in conse- 

 quence is considered to be an important factor in 

 forecasting droughts. 



Focal Depths of Earthquakes. — The first 

 number of the Geophysical Supplement to the 

 Monthly Notices of the Royal Astronomical Society 

 (for March 1922) consists of a valuable paper by 

 Prof. H. H. Turner on the arrival of earthquake 

 waves at the antipodes and on the measurement of 

 the focal depth of an earthquake. To a distance 

 A =90°, the usual tables give good results for the 

 arrival of the primary waves of an earthquake. 

 Beyond this distance there is some uncertainty, but 

 near the antipodes of the epicentre the records again 

 become clear and regular. From 130° to 180 the 

 time of traverse in seconds is given approximately by 

 the expression 



1217 - (180 -A) 2 x 0-0235. 

 For a single earthquake, the mean error of the 

 expression is about ±3-5 sees., but for the great 

 earthquakes from 1913 to 1916 it is about ± 14 sees. 

 There is thus a systematic error for each particular 

 earthquake ascribable to a particular depth of focus, 

 which must be greater than 0-021, and may have a 

 value such as 0-04, of the earth's radius. Prof. 

 Turner suggests that the antipodes of the epicentre 

 should be called the hypocentre, a term which has 

 been used for the last thirty years to denote the 

 seismic focus. In Italy its use for this purpose is 

 prai tically universal. Outside that country, it has 

 been adopted by M. de Montessus de Ballore and 

 Prince Galitzin. 



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