442 



NATURE 



{March 6, 1884 



seen ifsuiiior from the summit of the volcano ; and in tlie day- 

 time vast vohimes of smoke roll from it. Upon nearer approach 

 from P'nylii-h Harbour it was found that the mountain had lecn 

 split in two from peak to base by a great rupture extending 

 across it from east to west, and that the northern i-lope of the 

 mountain had nmk away to the level of the northern cliff.' This 

 is corroborated by the statement of the hunting-party in 

 Kami>hak Bay. Smoke issued from the peak at a very short 

 distance to the southward of the rupture. 



The party of natives on Kamishak did not approach the islet, 

 though they gave clear and distinct accounts of its eruption and 

 sulisequent appearance ; but Capt. C. T. Sands, who was at 

 English Harbour, gave the Alaska Company a full description ; 

 and Capt Cullie, of the Kodiak, states that, if there were plenty 

 of w ater in the line of rupture, it would be possible for a yes; el 

 to sail through. At the time of Capt. Sands' observations tlie 

 low ground of the island was visible, and seemed to be a vasit 

 crati r, from which smoke and flames were issuing. 



But beyond all these phenomena, apart from the volcanic 

 eruption and the rupture of the island, we have the report of 

 Capt. Cullie, of the.-chooner Amft?/- (from whom we also obtain 

 a statement in regard to the rupture), who approached the island 

 from English Harbour on November lo, and found that a new 

 island about a mile and a half long and seventy-five feet high, 

 had been upheaved in the ten-fathom passage between Augusiin 

 and the mainland to the westward. This passage is from six to 

 eight miles w ide, and was sailed through by Puget in Vancouver's 

 voyages of discovery. 



This new island (also reported by the hunting-party in 

 Kamishak) w ould appear to have arisen during the late volcaiiic 

 activity. It lies to the north-westward of Chemaboura Island 

 (AuJustin>, and was distinctly seen frcm the Kodiok, as that 

 vessel lay ten miles to the norlh-eattward, and had clear 

 weather. 



To show the violence of the volcanic convuhicns at this tiir.e, 

 two extinct volcanoes on the Alaska ]:eninsub, which are 

 repcrled to be about west (true) frcm the active volcano liianna 

 (twelve thousand feet high), had lurst into activity ; and during 

 the day volumes of smoke were distinctly seen, and columns of 

 flame at night. Usually, at that season, Augustin and the peak 

 are covered with deep snow. On November lo, however, when 

 Capt. Cullie apjixaohed the i'land, whie there was a dej-th of 

 four feet of snow at Tort Graham (English Harlour), Mount i-t. 

 Augustin was bare and black. 



George Davidson, 

 Assistant U.S. Coast and Geodetic Survey 



THE ORIGIN OF THE SCENER Y OF THE 

 BRITISH ISLANDS^ 

 'T'HE Plains of Britain, like those elsewhere, must be regarded 

 as local base-levels of denudation, that is, areas where, en 

 the whole, derudation has ceased, or at least has become much 

 less than deposit. Probably in all cases the ai-eas they occupy 

 have been levelled by denudation. Usually a gieater or less 

 depth of detrital material has been spread over them, and it is 

 the level surface of these superficial accumulations that forms the 

 plain. But in some instances, such as the flats of the Weald 

 Clay and the Chalk of Salisbury Plain, there is hardly any such 

 cover of detritus, the denuded surface of underlying rock 

 forming the actual surface of the plain. Our plains, if classed 

 according to the circumstances cf their origin, may he con- 

 veniently regarded as (I) river plains— strips of meadow-land 

 bordering the streams, and not infrequently rising in a succession 

 of terraces to a considerable height above the present level of the 

 water; (2) lake plains — tracts of arable ground occupying the 

 sites of former lakes, and of which the number is ever on the 

 increase; (3) marine plains— mostly flat stivages of alluvial 

 ground, formed of materials originally laid down as a littoral 

 marine deposit when the land lay below its present level : in 

 the northern estuaries these up-raised sea-beds spread out 

 as broad carse-lands, such as those of the Tay, Forth, and 

 Clyde ; (4) glacial drift plains— tracts over which the clays, 

 sands, and gravels of the Ice Age form the existing surface ; (51 

 submarine plains— the present floor of the North Sea and of 



^ Capt. CuIIie's account. 



= .'ibstiact of fifth .-md ccnclutling lecture ly Archibald Geikie, FR.S,, 

 Director-Geneial of the Geological Survey, gi%en at the Royal Institution. 

 March 3, Contiirued from p. 420. 



the Irish Sea, which must be regaided as essentially part of the 

 terrestrial area of Europe. 



When plains remain stationary in level, they may continue 

 for air indefinite period with no material ch.ingo cf surface. But, 

 should they be upraised, the elevation, by increasing theslopeof 

 the streams, augments their en, sive power, and en.it lesthem ^nce 

 more to deepen their channels. Hence, plains like that of the 

 New Forest, which have been deeply I rei ched by the water- 

 courses that traverse them, m.ay with probability be assigned to 

 a time when the land stood at a lower level than it occupies at 

 present. In this connection the successive river-terraces of the 

 country deserve attention. They may be due not to the m.ere 

 unaided work of the rivers, but to the cooperation of successive 

 U| lifts. It would be an interesting inquiry to correlate the 

 various river-terraces throughout the country, for the purpose of 

 discovering whether they throw any light on the conditions 

 under which the most recent uprise of the country took place. 

 That the elevation proceeded intermittently, with long pauses 

 between the movements, is shown by the succession of raised 

 beaches. It may be possible to establish a somewhat similar 

 proof among our river-terraces. 



The submarine plains are by far the most extensive within the 

 British area. In the case of the North Sea the tendency of tidal 

 scour and deposit must modify the form of the bottom. This 

 great basin of water is obviously being slowly filled up by the 

 deposit of sediment over its floor. A vast amount of mud and 

 silt is borne into it by the rivers of Western Europe, as well as 

 by those that drain the eastern and larger part of Britain, and the 

 sea it: elf is cutting aw ay the land on both sides and sw allowing up 

 the waste. Wehaveonly to contrast the colour of the Atlantic on 

 the v\est of Ireland or Scotland wah that of the North Sea to 

 be a:sured of the wide diffusion of fine mud in the water of the 

 latter. There is practically no outlet for the detritus that is 

 thus poured into the basin c f the North Sea. From the north a 

 vast body of tidal water enters between Scotland and Norway, and 

 travelling southward, aided l.y the strong northerly winds, sweeps 

 the detritus in the :ame direction. On the other hand, .inother 

 narrower and shallower tidal stream enteis from the .Strait of 

 Dover, and, aided by the south-west winds, drives the sediment 

 northward. Yet, making every allowance for the banks and 

 shoals which tl is accumulating deposit has already foru ed, we 

 can stil', without much difficult)', recognise the broader features 

 of the old land-surface ihat now lies subn erged beneath the 

 North Sea. It presents two plains, of which the southern has 

 an average level of perhaps a little nore than 100 leet helow 

 the surface of the water. This upper plain ends northward in a 

 shelving bank, probably the prolongation of the Jurassic escr.rp- 

 ment of Yorkshire, and is succeecled by the far wider northern 

 plain, wh'ch lies from ico to 150 feet lower, and gradually slopes 

 northward. As mentioned :n a previous lecture, the drainage- 

 lines of the united Rhine, Thames, &c , en the one side, and 

 the EHe, Weser, &c., on the other, can still be partially traced 

 on the sea- floor. The Irish Sea was pr-obably, in its later 

 history, a plahi dotted with lakes. It appears to have been 

 submerged before the whole of the present fauna and flora had 

 reached Ireland. 



S.on.e of the most characteristic and charming scenery of the 

 British Islands is to be found along their varied sea-board. 

 Coast-; ceneiy appeal s to de[ end for its di.--linctive features upon 

 (l)thefoimof the ground at the time when by emergence or 

 submergence the present level was established; (2) the compo- 

 sition and structure of the shore-rocks; (3) the direction of the 

 prevalent winds, and the relative potency of subaeiial and 

 marine denudation. The British coast-line presents three dis- 

 tinct phases : in many places it is retreating ; in others it is 

 advancing ; while in a few it may be regarded as practically 

 stationary. As examples of retreat, the shores of a large part 

 of, the east of Englai d may be cited. In Holderness, for 

 instance, a strip of land more than a mile broad has been carried 

 a« ay during the last eitht centuries. Even since the Ordnance 

 Survey maps were published, thirty-three years ago, somewhere 

 abcut 500 feet have in some places been removed, the rale of 

 demolition being here and there as much as five yards in a year. 

 The advance of the coast lakes place chiefly in sheltered bays, 

 or behind or in front of projecting headlands and piers, and is 

 due in large aeasure to the deposit of material which has been 

 removed by the sea from adjoining shores. The amount of 

 lard thus added does not compensate for the quantity carried 

 away, so that the total result is a perceptible annual loss. The 

 best examples of a s'ationary ccast-line where there is no appre- 



