254 



HARDWICKE'S SCIENCE-GOSSIP. 



Silurians might have been encountered there. We 

 are therefore right in assuming that the Devonians 

 have thinned out at some point between the two 

 borings, as A in the diagram. 



If we continue the angle of dip along the base of 

 the gault, supposing the strata to remain regular 

 at this angle of dip, we should probably not have 

 to proceed many miles before arriving at carboni- 

 ferous strata, outcropping, perhaps as at B. Whether 

 such strata would actually contain coal could only be 

 ascertained by experiment, since possibly the denuda- 

 tion of the palaeozoic land-surface which took place 

 prior to the deposition of cretaceous beds, may have 

 swept away in this particular place all traces of coal- 

 measures. 



In two of the three important borings which follow, 

 the precise age of the deepest-seated rocks has not 

 been satisfactorily determined. 



Beneath the gault, beds of Jurassic age have been 

 met in the borings at Meux's and at Streatham, at 

 a depth of 992 ft. in the former case, and at 1081J ft. 

 in the latter. Meux's boring has also furnished 

 undoubted upper Devonian rocks at 1056 ft. This 

 must respresent a rise of these rocks out of the trough 

 into which they were seen to be sinking between 

 Ware and Turnford, and which probably continued 

 beneath the Kentish Town boring. 



At the Kentish Town, and Streatham borings, beds 

 which have been classified in Mr. Whitaker's work on 

 the geology of London as marl, red sandstones, clay, 

 etc., were bored into at depths of 11135 ft., and 

 1120 ft., respectively. Now the unsettled question 

 about these is, are they also Devonian, or may they 

 be classed as new red sandstone or an abnormal 

 condition of any other series of strata? It is certain 

 that they are not of more recent age than Jurassic, 

 since at Streatham there is a thickness of 38J ft. of 

 Jurassic beds above them, and this narrows con- 

 siderably the question to be decided. They were 

 doubtfully classed when first discovered, and have 

 remained in doubt ever since, and we shall probably 

 have to wait a further boring somewhere nearer the 

 river, before a final decision is ventured upon. If we 

 consider the beds in both cases to belong to the 

 triassic series (new red sandstone), the strata may 

 possibly have a trend as shown in Fig. 153. There 

 can be no doubt that since the deposition of the 

 cretaceous beds there has been a considerable 

 crumpling of the earth's crust, and in order to allow 

 of the chalk reaching so near the surface as it does 

 at Meux's Brewery. Whatever contortion and 

 denudation the ancient palaeozoic beds may have 

 undergone previously, they must also have partaken 

 in the post-cretaceous flexures, which may very 

 possibly have brought about the position shown as the 

 position of these beds in the diagram, if regarded as 

 of triassic age. The position of the doubtful beds in 

 the Streatham boring would be easy of explanation, 

 in fact, here it would matter little if they eventually 



proved to be Devonian, as we have no evidence as 

 to where the Devonian dips again into a trough, and 

 it is only fair to say that they as much resemble the 

 one formation as the other. 



But, supposing on the other hand, the red clay and 

 sandstones in the Kentish Town boring are decided 

 to be Devonian also, the palaeozoic beds would then 

 appear to present much the same contortion as the 

 more recent secondary beds. As, however, the older 

 beds, when they appear at the surface in the coal- 

 producing areas at home and abroad, appear to have 

 been contorted and subsequently denuded so as to 

 leave them in isolated basins, as they may be termed, 

 separated, as Godwin-Austen has pointed out, by 

 intermediate areas exhibiting the outcrops of still 

 more ancient rocks, we can scarcely expect that the 

 position and shape of the cretaceous beds above is 

 closely imitated by the Devonians beneath, and for 

 this reason alone we should hesitate to class the rocks 

 in question as Devonian, unless they are decided to 

 be so from petrological or palieontological reasons. 

 The alternative being that they are of triassic age, 

 it sbould be pointed out that the position they must 

 then necessarily occupy would agree with precon- 

 ceived opinions as to the contortion and denudation 

 of the palaeozoic land-surface previous to the deposi- 

 tion of the secondaries. 



In a distance such as that between Turnford 

 (Cheshunt) and Kentish Town, one cannot tell what 

 may happen in the configuration of these ancient 

 strata. Mr. Whitaker has pointed out that even 

 between Ware and Turnford, it is quite possible that 

 a trough may occur such as that shown in Fig. 152, 

 by means of which a patch of carboniferous strata 

 may still remain, which has since been unconformably 

 covered by the gault. Such a dip, however, is not 

 at present shown by any knowledge which has been 

 actually obtained. It illustrates, however, how car- 

 boniferous beds might possibly be met with, either 

 here or perhaps beyond the Streatham boring, a 

 region where the ancient rocks have not at present 

 been bored into. 



In referring to the accompanying diagrams it must 

 not of course, be overlooked that the scale used is 

 one which exaggerates tremendously the depth of the 

 strata in proportion to the extent of surface shown. 

 A true representation would be secured were the 

 horizontal distance multiplied about fifty-three times, 

 but this is obviously impossible in the case of a 

 simple diagram. 



Copper and German silver wire "002 inch in 

 diameter, of which it takes ten miles to weigh a 

 pound, is used in the delicate receiving instrument 

 for ocean cables, testing galvanometers, etc. Small 

 as the wire is, it is wound with two layers of silk 

 thread smaller in diameter than the wire. The wire 

 is made by drawing through drilled diamonds. 



