HA R D WICKE ' S S CIE NCE - G O SSIP. 



lo- 



in no parts of the so-called Skiddaw slate area are 

 good workable slates met with. This slaty structure, 

 it will be known to many of my readers, is one that 

 has been produced in the rock by agencies called into 

 play long after the first formation of the rock, and of 

 these we shall speak in a future chapter; for the present 

 suffice it to say that a rock is said to be cleaved, or 

 subject to slaty cleavage, when it will split more or less 

 readily into thin plates, irrespective of other divisional 

 planes. In the mountains of Whiteside and Grasmoor, 

 overlooking the Vale ofLorton and Crummock Water, 

 the formation is represented by beds of sandstone and 

 fine grit, whilst in various scattered localities the 

 rock is a coarse grit. The matter of the mountains 

 in this most northern area consists therefore of slate 

 (or sometimes even black shale), sandstone, and 

 grit. Besides these there are occasional small or large 

 areas of rock in the direct formation of which heat, 

 more or less intense, has played a part, and such we 

 call (a) igneous (fiery), and (i) metamorphic (changed) 

 rocks, and these have either (a) been thrust through 

 the surrounding rocks, or {b) consist of the same rock 

 as that around, very much altered by heat acting 

 under pressure. But our slate, sandstone, and grit, 

 how were they formed ? Have they anything to do 

 with heat ? Not directly, though we have already 

 hinted at the slaty structure having been produced 

 by physical agencies, of which lateral pressure seems 

 to have been the chief, and there can be no pressure 

 exercised without heat to a certain degree being pro- 

 duced. But we must cease to look at the rock as a 

 slate and seek for evidence of its original mode of 

 formation. Such a search reveals the fact that we 

 have here what was originally mud, for in some parts 

 of the district the rock* is very soft and shaly, 

 very much like the black shales of the coal measures, 

 and so much so indeed as to have led in former times 

 to the sinking of pits with the hope of reaching coal, 

 a waste of money, which would have been at once 

 checked by even a small amount of geological know- 

 ledge. In some parts also the rock is seen to be 

 clearly traversed by fine parallel bands or lines, some- 

 times of slightly different colours, precisely similar to 

 the banding we may observe in a mud-bank which 

 has been cut into at the mouth of a river. Such an 

 appearance leads us to suspect the aqueous (or 

 watery) origin of the rock, and we are confirmed in 

 our surmise by finding here and there the entombed 

 remains (fossils) of various forms of life, just as we 

 might find in our mud-bank buried shells and sea- 

 weeds. Moreover, on comparing the forms of these 

 fossils with those of existing life, we come to the con- 

 clusion that for the most part they represent ancient 

 marine life, and that the mud rocks of the Skiddaw 

 slate formation were laid down probably in a more 

 or less shallow sea. Examination of the sandstone 



* All matter entering into the composition of the earth in 

 mass is called in geological language rock, whether hard or 

 soft. 



and the grit still further confirm this idea ; they also 

 occasionally contain marine fossils, and show con- 

 clusively by this bedding and current (or ripple) 

 marked surfaces, that they were laid down beneath 

 the shallow waters of the ancient Skiddaw slate sea, 

 if we may so term it. Such deposits at the present 

 day, however, are shore deposits, although occasionally 

 the waters of a mighty river, such as the Amazon, 

 may carry out fine mud in suspension, several hundred 

 miles from land. Pebbles forming conglomerate and 

 sand forming sandstone, are deposited nearer shore 

 in shallower water. 



This, then, is the origin of the group of rocks now 

 called the Skiddaw slate — land washings, as we may 

 term them from some tract of continental land, 

 deposited over that part of the earth's surface, a 

 portion of which is now occupied by our present Lake 

 District. To the reader unaccustomed to geological 

 thought it may be difficult to lose sight of the present 

 surface and configuration of land, but this he must 

 completely wipe out from his mind and conceive all 

 as from the commencement of the geological history 

 in this district. In which direction the land lay from 

 which these sedimentary deposits were borne it is 

 difficult to say with any certainty, but, inasmuch as 

 on the whole the gritty beds increase westwards 

 (being perhaps more developed in the Isle of Man 

 than in West Cumberland), one may hazard a con- 

 jecture that the land lay to the westward. 



One word with regard to the thickness of this 

 series of deposit. It is impossible to measure the 

 entire thickness of this formation, because one knows 

 of no defined base to the series, and the difficulty is 

 much increased by the wonderful manner in which 

 the beds are contorted and curved ; nevertheless by 

 taking some of the more regularly bedded and little 

 contorted parts, one is able, by measuring across the 

 beds — as across those of Whiteside in the horizontal 

 section given in the last number (fig. 54) — to make a 

 guess at the probable total thickness, and this I am 

 inclined, after examination of the whole Skiddaw 

 slate area, to put down as not less than 10,000 feet. 

 Let us think for a moment what this means. The 

 deposits being mud, sand, and pebbles, are, in the 

 main, shore deposits ; moreover it is not the case that 

 the coarser beds are confined to the top of the series 

 and the finer to the base ; for if it had been so we 

 might have fancied that the first layers of fine mud 

 were deposited in a deepish sea far from land, which 

 gradually became more shallow, principally by the 

 deposition of this great thickness of beds, so that at 

 length the coarser material would come to be laid down 

 in the shallowest sea. It would seem rather, that 

 with the exception of a thin bed of conglomerate near 

 the top of the series, the coarser deposits are in most 

 force at the lower part of the series, so that it would 

 seem, we must assume, that the deposits generally 

 were laid down in a more or less shallow sea, the 

 deposition being accompanied by a gradual sinking 



