May 5, 1910J 



NATURE 



293 



being superseded in many minds by Chamberlin's 

 planetesimal theory, after having inspired petrologists with 

 a vain hope of finding traces of the primeval slaggy crust 

 among the Archaean gneisses. Astronomers prefer a solid 

 globe, but on grounds different from those assumed by 

 Hopkins and at first accepted by Lord Kelvin. Arrhenius 

 concludes in favour of a gaseous core, like that postulated 

 by Ritter, but of larger dimensions than the gaseous core 

 sugS^^f^d by Dr. Wilde. 



Theories regarding the processes of consolidation, the 

 gradient of pressure, and the deep-seated rise in tempera- 

 ture are equally varied. Until this year all agreed in 

 assuming the earth's interior to be hot, but Prof. Schwarz 

 now prefers to think it is cold. So long as radio-active 

 bodies were unknown the apparent reserves of heat-energy 

 offered the world a short life ; but its actuarial value has 

 now been increased almost indefinitely by the discover>' 

 of radium in embarrassingly large quantities, and Prof. 

 Joly warns us that, instead of peaceful cooling, the present 

 " age " may end in catastrophic heating. 



The nearest approach to actual observation regarding 

 the deep-seated parts of the globe is recorded by the 

 seismograph as interpreted by R. D. Oldham, who aptly 

 compares the seismograph with the spectroscope as an 

 instrument for examining inaccessible objects. The first 

 and second phases of long-distance seismographic records, 

 which are due to waves passing through the earth by 

 approximately chordal paths, show a reduction in velocity 

 when there is a sufficient distance between the origin of 

 the shock and the recording instrument for the assumed 

 chordal paths to pass through the inner two-fifths of the 

 earth's core, while the distortional waves are apparently 

 dispersed by refraction when the origin of the earthquake 

 and the recording instrument are separated by about 140°. 

 The records, which are confessedly too few to be regarded 

 as conclusive, suggest that the central core differs in 

 physical characters from the outer three-fifths and the 

 superficial crust. Similarly, the vibrations that pass under 

 the great oceanic depressions indicate elastic conditions 

 differing from those under the continental plateaux, the 

 difference being apparent to a depth of about one-quarter 

 the earth's radius. This last conclusion might be corre- 

 lated with the variation in the chemical composition in 

 the sub-oceanic crust caused by selective denudation of the 

 kind indicated by Sir John Murray in 1899. and by 

 Chamberlin's theory regarding the origin of the oceanic 

 depressions. 



The recent discussions and new data obtained by 

 geodesists and geologists to check Dutton's theory of 

 Isostasy have revived interest in the deep-seated parts of 

 the superficial crust. The remarkable work recently done 

 In India by Burrard and Lenox-Conyngham, when corre- 

 lated with the results of the Geological Survey, are 

 especially important in showing the truth and the limita- 

 tions of isostasy. Burrard 's results indicate that the 

 Himalayan heights are partly compensated by deficiencies 

 of subterranean gravity, and that greater lo-ads are main- 

 tained by the rigidity of the geologically st.ible crust of 

 the peninsula than in the folded parts of the extra- 

 .peninsular region. The deficiency of gravity under the 

 outer and sub-Himalaya is, however, equally pronounced 

 in the plains near the southern foot of the range ; but at 

 a distance of about 150 miles from the foot of the moun- 

 tains there is a subterranean band of high gravity parallel 

 to the alluvium-filled Gangetic valley, as well as to the 

 four Himalayan zones — the foot-hills, composed of Tertiary 

 strata ; the outer Himalaya, of much older, unfossiliferous 

 sediments ; the crystalline range of snow-covered peaks ; 

 and the Tibetan highlands of fossiliferous, marine strata. 



Soon after Dutton published his theorv of isostasy, R. S. 

 Woodward pointed out that, if the highlands continued to 

 rise in consequence of the reduction in their load by 

 erosion, and the depressions continued to sink under the 

 growing weight of accumulating sediment, the process 

 should continue indefinitely, and mount.nin ranges would 

 thus never be worn down, while new folds in undisturbed 

 areas would never arise ; but the geological history of 

 India shows whv and how this process may result in 

 " isostatic suicide." For ages before the end of the 

 Mesozoic era the rivers of Gondwanaland, which stretched 

 away as a great continent to the south and west, poured 



NO. 2 114, VOL. 83] 



their loads of silt into the Eurasian ocean, of which the 

 southern shore-line approached the line now occupied by 

 the Himalayan snow-covered peaks. With the loading 

 down of the northern littoral of Gondwanaland, the northern 

 part of the continent became stretched, and normal faults 

 were developed with a general east to west trend. 



Some of the faults of this kind occurring in the Central 

 Provinces were shown by J. G. Medlicott, so long ago as 

 i860, to be pre-Gondwana (that is, pre-Carboniferous) in 

 age, others were formed before the Upper Gondwana 

 (Lower Mesozoic) strata were formed, while the latest 

 affected the younger Gondwana beds, and became channels 

 for the Upper Cretaceous basalts. The general trend of 

 the Cretaceous dykes in this part of India, and the pre- 

 valence of normal faults further east at about the same 

 latitude, shown in various geological maps published by 

 later members of the Geological Survey, indicate the 

 nature and direction of the tension produced by the un- 

 loading of Gondwanaland and the simultaneous depression 

 of the adjoining ocean bed. The process reached its 

 climax towards the end of Cretaceous times, when the 

 basaltic magma below welled out and flooded more than 

 200.000 square miles to a depth of nearly a mile. 



Presumably the tension marked by faults in Central 

 India existed also in areas further north, where the records 

 are now buried under the Gangetic alluvium, and the band 

 of high gravity detected by Burrard 's plumb-line and 

 pendulum is probably due to concealed batholiths of basic 

 and ultra-basic magma, which were injected into the region 

 of tension after the manner described by Prof. R. .A. Daly.' 

 Then followed the production of a geosyncline parallel to 

 the northern shore-line of the old Gondwana continent and 

 parallel to the subsequent folds of the Himalayan range, 

 which are now being thrust over towards the region of 

 deficient gravity between the visible mountain range and 

 the concealed band of basic batholiths. 



The data in this area are in substantial agreement with 

 Daly's idea of a persistent sub-crustal gabbroid magma, 

 which, though possibly only in a state of potential fusion 

 under regions of normal pressure-gradient, may become 

 fluid in localities of protracted erosion and gradual rise of 

 the northern shore-line of the old Gondwana continent and 

 agree, in general, with those analysed by Hayford and others 

 in America in showing that isostasy can be detected only 

 when the visible masses over wide areas are concerned ; 

 further data of this kind will permit of the determination 

 of the minimum loads that can be maintained by the crust 

 in old stable land surfaces as compared with the apparently 

 smaller loads maintained in recently folded regions. If the 

 sequence of events in India has been correctly traced, it 

 should be possible to indicate areas on the earth which 

 are in danger of b.isaltic floodings and of later folding 

 movements. In South .America, for instance, the north- 

 flowing tributaries of the .Amazon and the .Araguaya are 

 possibly developing conditions on the old land surface of 

 Brazil similar to those that on Gondwanaland preceded the 

 outburst of the Deccan Trap in Cretaceous times. 



THE HULA, OR FOLK-DRAMA OF HAWAIL 



'T'HE Hula, or national folk-drama of Hawaii, has 

 already been casually described by the Rev. W. Ellis 

 in his '* Polynesian Researches," and has been noticed in 

 the " Travels " of Captain Cook ; but it was left to Dr. 

 X. B. Emerson to undertake a detailed investigation of 

 the unwritten literature of the island, and to make a 

 collection of the songs sung in these performances. The 

 results of this study . have been published in Bulletin 

 No. 38 of the American Bureau of Ethnology'. We may 

 congratulate this institution on having now, for the first 

 time, linder the authority of a special Act of Congress, 

 extended its operations beyond the bounds of the American 

 continent. 



The Hula is a special form of folk-drama, dealing in a 

 series of impassioned lyrics with many phases of the 

 national mytholog\- and traditions. The poetry is of a 

 highly romantic and sensuous type, including themes con- 

 nected with human love and life, the processes of nature, 



1 " Aby<«al Inject'on as a Causal Condition and as an EflFect of Moantain- 

 building," by R. A. Daly (Amcr. Journ. Set., xxr,, 1906, pp. 2oj~t%), 



