NA rURE 



[August i, 1907 



ihus Ije brought about, we may examine a figure which 

 shows the composite elevations and depressions that an 

 reprpsenled by harmonics of the first and second degrees, 

 and, separately, those which are represented by harmonic 

 of the third degree. In Fig. 15 the composite elevations of 

 the first and second degrees are shaded vertically, and the 

 elevaiions of the third degree are shaded horizontally. '1 1 

 deep parts of the Atlantic that border the coasts every- 

 where from Brazil to Ashanti are regions in which a depres- 

 sion represented by the third harmonic is superposed upon 

 an elevation represented by the other two harmonics, and 

 ihe same is true of the deep parts of the Indian Ocean 

 which border the shores of Africa and Asia from Mada- 

 sjasrar to Burmah. The deep parts of the Pacific that 

 border the western coast of America from Alaska to Ch' 

 are regions in which an elevation represented by the third 

 harmonic is superposed upon a depression represented by 

 ihe other harmonics. These observations suggest that in Ihe 

 greater part of the Atlantic and the northern and western 

 pans of the Indian Ocean the direction of s;Ecular change 

 may have been that of an advance of the ocean to encroach 

 upon the continental region, while in the Pacific Ocean on 

 ihe .-Vmerican side the direction of saccular change may 

 have been that of a retreat of the ocean, permitting an 

 extension of the continental region. This difference would 

 lead us to expect different types of coast in the two 

 regions, and such a difference has been observed. Whereas 

 in Ihe Atlantic region, with few exceptions, the coast cuts 

 across the directions of the mountain chains, in the Pacific 

 region on the American side the coast generally corresponds 



Fig.15. 



in direction with the neighbouring mountain chains of the 

 continent. The deep parts of the Pacific which are nearest 

 to the Asiatic coast from Kamchatka to Siam are regions 

 where a moderate depression represented by the third har- 

 monic is superposed upon a moderate elevation represented 

 by the other harmonics. These shores of the Pacific are 

 dislinguished by the wide margin which separates the deep 

 ocean from the coast of the continent. It might perhaps 

 be desirable to recognise in this region a type of coast 

 differing from the two main types associated with the 

 Atlantic and the American side of the Pacific. The analysis 

 does not represent South Africa or the southern parts of 

 South America sufficiently well to warrant us in expecting 

 these regions to exhibit one type rather than the olher ; 

 but the way in which Australia is represented, as an ele- 

 vation of the third degree superposed upon a depression of 

 the first, suggests that the coasts of Australia, and especially 

 the eastern coast where the elevation in question is 

 greater, should be of the same type as the American shores 

 of the Pacific; and it is the fact that the mountain chains 

 of Queensland and New South Wales run parallel to the 

 neighbouring coasts. There seems therefore to be much 

 evidence to support Ihe view that the direction of sjEcular 

 change has been that of diminishing the prominence of the 

 inequalities of the first and second degrees in comparison 

 with those of the third degree. The process by which such 

 changes would be brought about would be of the nature 

 of relief of strain, expressing itself in occasional fractures 

 of no very great magnitude ; and such fractures would be 

 manifested at the surface as earthquakes. Seismic and 

 volcanic activities constitute the mechanism of the process 

 of change. These activities are spasmodic and irregular, 

 but the effect of them is cumulative. For this reason thev 

 tend in the course of ages to transform the shape of the 

 NO. 1970, VOL. 76] 



earth from one definite type to another. The diminishing 

 speed of the earth's rotation is another cause of change 

 which appears to produce an allernating rather than a 

 cumulative effect. On the one hand it tends to diminish 

 that tendency, which we noted above, to draw the waters 

 of the ocean towards equatorial regions ; on ihe other hand 

 it must result in an actual reduction of the equatorial 

 protuberance of Ihe earth's figure. This reduction can only 

 be effected by seismic activity expressed by subsidences in 

 equatorial regions. The effect which would in this way 

 be produced in the distribution of continent and ocean 

 would appear to be that there would be long periods in 

 which the ocean would tend to advance towards the Arctic 

 and Antarctic regions, interrupted by shorter periods in 

 which it would tend to retreat towards the neighbourhood 

 of the equator. 



The theory which I have tried to explain is a tentative 

 one, and further investigation may prove it to be untenable : 

 but it is to its credit Ihat, besides tracing to dynamical 

 causes the existing distribution of continent and ocean, it 

 offers an explanation of the difference between the .Atlantic 

 and Pacific types of coast, it gives indications of a possible 

 account of those alternations of sea and land which first 

 led to the study of geology, and it suggests an (rigin for 

 Charles Darwin's unknown force the operation of which is 

 slow and intermittent, but irresistible. 



Xkxt year's meeting of the British Medical .Association 

 will be held at Sheffield under the presidency of Mr. Simeon 

 Snell. This year's meeting is at present in progress at 

 Exeter. On Tuesday last the president. Dr. Henry Davy, 

 delivered his address, taking as his subject " Science in 

 its Application to National Health." 



The Nimrod, in which Mr. E. H. Shackleton's expedi- 

 tion will proceed to the -Antarctic regions, sailed from the 

 Thames on July 30 with Lieut. Rupert England in com- 

 mand. Lord Kelvin has presented to the expedition a 

 standard compass and sounding instruments. The 

 .Admiralty is lending a compass, chronometers, charts, and 

 sounding apparatus, as well as three Lloyd-Creak Dip 

 instruments for the landing party. Watches are being 

 suppli'ed by the Royal Geographical Society, and, in 

 addition, the vessel will be equipped with a liquid steer- 

 ing compass and a special pole compass. The members of 

 the expedition on board the Nimrod are Mr. James Murray, 

 the biologist of the expedition ; Mr. \V. .\. Michell, surgeon 

 and zoologist ; and .Mr. A. F. Mackay, the junior surgeon 

 of the landing party, who will also engage in zoological 

 work. At Lyttelton, New Zealand, the remaining members 

 of the expedition will join the ship. These include, besides 

 .Mr. Shackleton, .Mr. E. Marshall, senior surgeon of the 

 shore party and cartographer of the expedition ; Lieut. 

 -Adams, R.N.R., who will be in charge of the meteor- 

 ological work ; and Sir Philip Brocklehurst, for survey 

 work and field geology. Dr. David, professor of geology 

 in Sydney University, has arranged to accompany the 

 expedition south to King Edward VH. Land. 



The weather still continues very cool for the time of 

 year, but on the whole the conditions lately have been 

 somewhat dry. .At Greenwich there has been no year 

 since 1888 with so few warm days in July, and the 

 thermometer has not once touched 80°. The total rain- 

 fall for the month is less than an inch, whilst the average 

 for the past sixty years in July is 2-40 inches. The 

 aggregate rainfall for the first eight weeks of suinmer, to 

 July 27, is less than the average in the north-east, east, 

 and south of England, and in the Channel Islands, but 

 in every other district of the United Kingdom it is in 

 excess of the normal. The greatest excess for the summer 



