January 15, 1920] 



NATURE 



5'9 



dates from the formation of the Arabian Sea and the 

 breaking up of Gondwanaland, which originally in- 

 cluded both India and Africa. These subsidences 

 became more rapid about the end of the Chalk period, 

 and led to volcanic eruptions on a colossal scale. On 

 the eastern side of the foundered area were discharged 

 the Deccan Traps, covering more than 200,000 square 

 miles in India, and probably an equal area under the 

 Indian Ocean. On the northern and western sides 

 volcanic eruptions probably contemporary with the 

 Deccan Traps formed the plateau-lavas of southern 

 -Arabia, Abyssinia, and the Kapite Plains in East 

 .Africa. These lava plains are older than the Rift 

 Valley faults, and after them the East African arch 

 fell in and initiated the Rift Valley ; then followed 

 eruptions from fewer vents building up higher vol- 

 canoes. They were followed by a lake period, the 

 age of which is fixed by the remains of Dinotlieriiun 

 Hobleyi as Miocene. 



That the whole volcanic history of British East 

 -Africa cannot be restricted to the post-Miocene is 

 indicated by the evidence of Mount Kenya, since the 

 glaciation of its valleys shows that they were in 

 existence, the mountain had been deeply dissected 

 before glacial times. It is incredible that the long 

 volcanic history of the country, from the oldest plateau- 

 lavas to the reduction of Kenya to its present form, 

 should be restricted to only one period, the Pliocene. 



If the first eruptions of the Rift Valley area were 

 contemporary with the Deccan Traps, and therefore of 

 the age of the Chalk, and the faulting lasted from 

 the Oligocene to the Pliocene, the formation of the 

 Rift Valley was connected with two great systems of 

 earth movements, the foundering of the Indian Ocean 

 and the uplift of the Alpine and Himalayan mountain 

 svstems. Durinsj the Mesozoic a slow deformation 

 of the earth's crust caused the downward sagging of 

 the North Polar regions and the buckling of the 

 tropical and temnerate zones by broad folds running 

 east and west. Then elevation on lines trending north 

 and south raised the East African highlands, while 

 the collapse of the floor of the Indian Ocean caused 

 widespread volcanic disturbances round the Arabian 

 Sea. Later earth movements, which lasted for about 

 the same time as the faulting of the Rift Valley, 

 buckled the crust into the fold mountains of Europe 

 and Asia. This corrugation was due to pressure, 

 which in Europe was northward and in Asia south- 

 ward. The reversal of direction may be explained 

 bv the difference in structure between Eur-.Africa and 

 Asia. Africa was a high plateau undergoing further 

 uplift, while regional subsidence was taking place in 

 and off northern Europe. The combined subsidence 

 to north and uplift to south left Europe laterally un- 

 supported on the north : the crust north of .Africa was 

 pressed northward, and buckled the country in front 

 of it into fold mountain chains. In Asia the condi- 

 tions were reversed ; the massive plateau was to the 

 north, and the sinking area was to the south in the 

 Indian Ocean ; so .Asia was corrugated bv a south- 

 ward movement. The reversal from the European to 

 the .Asiatic direction occurred near the Sea of .Azov 

 and due north of the Rift Vallev, which is the rift 

 between the segment of the earth moving northward 

 and that movine: southward. 



The structural contrast between Africa and America, 

 due to the difference between the later mountain- 

 forminff movements, is exnlained by the fact that 

 Africa is antipodal to the Pacific Ocean, and by the 

 welLestablished principle that antipodal areas of the 

 crust are subiect to contrary conditions. While the 

 Pncifi'- was sinking. Africa was being upraised. The 

 "subsidence of the Pacific buckled its borders into the 

 fold mountain chains of Western .America, and those 



NO. 262c, VOL. 104] 



of which fragments can be traced from Japan to 

 New Zealand. As Africa was being stretched by its 

 uplift, and left unsupported on each side by the 

 foundering of the adjacent oceans, it was rent by 

 fractures between which the summit of its highlands 

 fell in and formed the Great Rift Valley. "There 

 may," says Sir George Adam Smith, "be something 

 on the surface of another planet to match the Jordan 

 Valley; there is nothing on this." That remark 

 may be extended to the whole Rift Valley ; for, in 

 addition to the other unique features of Africa, its 

 Rift Valley has no parallel elsewhere on the globe. 

 The character of that valley may be explained by the 

 special stresses in Africa due to its position antipodal 

 to the great subsidence of the Pacific Ocean, while 

 its course was determined by the wrench in the crust 

 between the segment in which the pressure was north- 

 ward against Europe and that pressing southward 

 from the Asiatic highlands towards the infallen basin 

 of the Indian Ocean. 



A 



PHYSIOLOGY AT THE BRITISH 

 ASSOCIATION. 



JOINT discussion with Section F (Economic 

 Science and Statistics) and the Subsection of 

 Psychology on "The Influence of the Six-hour Day 

 on Industrial Efficiency and Fatigue " was opened 

 by Dr. H. M. Vernon. It has been suggested by 

 Lord Leverhulme that two six-hour shifts may be 

 more economical than one eight-hour shift, because 

 the former would obtain twelve hours' use of expen- 

 sive machinery instead of only eight hours. Examples 

 were given of cases in which shortening of the 

 hours of labour had increased the output, but in 

 other cases the output had been decreased. The 

 determining factor seems to be the amount of mus- 

 cular effort put into the work. Heavy muscular work 

 can be speeded up for shorter hours to produce a 

 greater output, but where heavy labour is not involved 

 the production falls with shorter hours. 



Mr. P. Sargant Florence gave statistics from the 

 United States which supported the concluding portion 

 of Dr. Vernon's paper. He further pointed out that 

 the average age of the working population should be 

 taken into account as indicating whether the labour 

 was too long or too heavy. Noise in factories is 

 particularly fatiguing. 



Prof. E. L. Collis advocated a reduction of working 

 hours for the sake of health, but said that it must 

 be done slowly. Unequal distribution of wealth is 

 being remedied, but output must be increased. 



Sir Hugh Bell pointed out the difference between 

 various trades. Where the labour bill is only a small 

 part of the cost of the manufactured article, it is easier 

 to increase wages than when wages form the main 

 portion of cost. He objected to legislation and un- 

 informed interference, because agreement between 

 employers and employees had reduced the hours of 

 labour without the bad effects of legislative inter- 

 ference. 



Miss C. Smith-Rossie advocated a wider educa- 

 tional system on the lines followed by Denmark, so 

 that more interest can be aroused in the working 

 peoole. thus eliminating fatigue. 



Dr. H. H. Dale opened a discussion on "The Rdle 

 of Capillaries in the Regulation of the Blood-flow." 

 Previouslv the control of the blood-pressure had been 

 considerecl to be brought about by the state of con- 

 traction of the arterioles, but it is now necessary to 

 discuss whether the capillaries may or mav not take 

 some pan in the regulation. Small doses of histamine 



