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HARDWICKE'S SCIENCE-GOSSIP. 



the town of Keswick so prettily nestles, was the only, 

 or even the chief, centre^of the district ; there may 

 have been but one, or there may have been several. 

 Certain it is that lava-flows prevail more among 

 the exposures of volcanic rock, within six or seven 

 miles of Keswick, than u they do in any other part 

 of the district ; but this may be partly because the 

 lower portions of the series which contain more lava 

 than the upper, are here mostly represented. How, 

 then, are we to carry on our history from the close 

 of the Skiddaw slate period ? Generally, where the 

 lowest volcanic beds of the series are seen they are 

 found to alternate with beds of the Skiddaw series, 

 and in one or two cases some of the lowest ash-beds 

 are decidedly conglomeratic, that is to say, the 

 fragments have been rounded, by having been rolled 

 under water. These two facts clearly indicate that 

 the first showering down of ash, and flowing out of 

 lava, took place beneath the waters of the shallow sea. 

 How long this lasted it is difficult to say, but in all 

 probability a volcanic cone soon showed itself above 

 the waters, and its growthTmay have been accom- 

 panied — as is frequently the case with volcanic 

 districts — by a gradual elevation of the whole area, 

 so that after a while the greater "part of the volcanic 

 deposits were thrown down upon dry land. It may 

 have been, however, that some of the very finely- 

 bedded deposits were accumulated beneath water 

 at some distance from the centre of eruption, or 

 possibly in crater-lakes. No fossils are, however, 

 found in any of these bedded volcanic rocks, while 

 in submarine volcanic rocks of somewhat similar age 

 in Wales they are not infrequent. On the whole, 

 considering that we have here, as I have been led to 

 estimate, probably 12,000 feet in thickness of these 

 volcanic rocks, without any trace of ordinary mud, 

 sand, or grit-beds amongst them (except quite at the 

 base), and altogether devoid of fossils, I think it is 

 easier to conclude that the mass represents in the 

 main the products of a land volcano, no trace of the 

 original form of which, as already stated, is now 

 left. 



We must infer from what we have learnt of the 

 Skiddaw sedimentary series that the period of time 

 represented by that formation must have been very 

 great ; how great, it is difficult with any accuracy to 

 estimate ; but when we come to consider the same 

 question of time with regard to the volcanic series 

 the difficulties are of a somewhat different kind. 

 Modern experience of volcanic action seems to show 

 that, while sometimes the energy manifests itself 

 almost continuously, and sometimes with great 

 violence, at other times the efforts are very spasmodic 

 and only occasionally great. From the general 

 apparent absence of great breaks (geologically called 

 unconformities) in the series, the deposits do indeed 

 appear as if they might have succeeded one another 

 without any very long intervals of time, and if this 

 were the case, this period may have been a shorter 



one than the preceding. Those who know some- 

 thing about the different classes of volcanic rock may 

 be interested to know that many of the lavas in the 

 lower part of the series (especially those of Eycott 

 Hill) are like true modern basalts ; whilst the 

 majority of the flows occurring higher up in the 

 series show intermediate characters between the 

 basalts and the trachytes. 



A word now about the close of this period. A 

 time came at last when the volcanic energy died out 

 beneath this particular tract. Observations of 

 modern volcanic phenomena seem to indicate that 

 when the volcanic fires have died out there frequently 

 follows a sinking of the area over, or near, which the 

 volcanic action has been displayed. Perhaps this 

 may be partly due to the mass of matter previously 

 thrown out from within, so that large hollows having 

 been left, a downward sinking of the crust above 

 succeeds, like the creep of the ground over a worked- 

 out coal area. 



But even apart from this, we know that movements 

 in one direction or another, upward or downward, 

 are constantly taking place over various parts of the 

 earth's surface. A movement of depression certainly 

 took place when the volcanic energy abated, a 

 depression it would seem, extending to below the level 

 of the sea, so that bit by bit the volcanic mountain 

 or area must have been gnawed into along the sea 

 margin, until, when the last of these deposits had sunk 

 beneath what to us is a new sea, large portions must 

 necessarily have been washed away (or denuded) by 

 the encircling waves, the consequence being that 

 the first ordinary sedimentary deposits of the next 

 period were laid down upon very various parts of the 

 old volcanic series. 



The first of these deposits which we shall have to 

 notice is a limestone bed, full of marine shells of no 

 great thickness, called the Coniston limestone, and 

 it is the outcrop of this particular bed which forms 

 the long, straight south-west and north-east boundary 

 line previously mentioned (see map) as dividing the 

 boldly mountainous area from that less so, in which 

 Coniston and Windermere lie. And I make special 

 mention of it here before closing this chapter because 

 in connection with it there occurs another faint 

 attempt at volcanic action, for, interbedded with the 

 limestone in some parts of its course, occurs, what 

 would appear to have been a flow of lava of highly 

 silicic character, perhaps answering to our modern 

 quartz-trachytes. This was the consequence of but 

 a slight submarine eruption, and is the last trace we 

 meet with in Lake District history of volcanic energy 

 displayed at the surface. 



To look back over the road we have thus far 

 travelled, or through the ages we have been passing, 

 let us remember that geological history begins in the 

 Lake District, with the conditions of a shallow sea 

 into which are carried deposits of sand and mud, the 

 bottom of that sea subsiding gradually as the beds 



