492 



NA TURE 



[September 19, 1S95 



being rather thin. This agrees with what is found in other parts 

 where the Chalk is thick, extra thickness being chiefly due to the 

 highest division. The glauconitic marly bed at the lase seems 

 lo be well developed and to be underlain by the Gault clay ; so 

 that we have no good e\-idence of the occurrence of Upper 

 dreensand. This division may be thinly represented at Milden- 

 hall, but it is diflicult to classify some of the beds |xissed through 

 in the old boring there. 



.■\s far as the Gault is concerned, little, of course, is known ; 

 but that little points to this formation being unusually thin, pre- 

 sumably only 73 feet from top to Ixiltom at Culford, and probably 

 not more than lietween 50 and 60 at and near Harwich. In the 

 north-western part of the neighbouring county of Norfolk it is 

 well known to be still less, the clay thinning out northward 

 along the outcrop, until at last there is nothing but a few feet of 

 Red Chalk between the carstone of the Lower CIreensand and 

 the Chalk. The Gault l>eing of much greater thickness around 

 and under other parts of the London Basin, this thinning in 

 Norfolk and Suffolk is noteworthy. The absence of the more 

 inconstant l'|iper ("<reensand is to be expected in most places, 

 and calls for no remark : it may, however, be noted that geo- 

 Ic^ts .are coming to the conclusion that these two divisions are 

 really parts of one formation, and one result of this geologic 

 wedding is for the inconstancy of one |)arlner to be greatly com- 

 jiensated by the constancy of the other. 



The Lou'/r Gretiisaiid has been found in one deep boring 

 only, at Culford, in the western |)art of the county, where it is 

 represented by yi\ feet of somewhat exceptional beds. This 

 .>.light thickness prepares us for underground thinning, and in the 

 far east of the county the formation is presumably absent, there 

 being no trace of it at Harwich or at .Stutton. 



With the Cretaceous beds we pass from the regular orderly 

 succession of geological formations ; indeed, it may be said that 

 when we reach the base of the Gault we ])ass out of the region of 

 facts into the realm of speculation. 



VVe have come, then, to perhaps the most interesting problem 

 in the geology of the Eastern Counties, to the consideration of 

 the question, WTiat rocks underlie the Cretaceous beds at great 

 depths ? In dealing with this I must ask your i>atience for fre- 

 quent excursions outside our special district, and sometimes 

 indeed far away from it. 



Beyond the outcrop of the lower beds of the Cretaceous Series 

 in Cambridgeshire and Norfolk, we find of course a powerful 

 development of the great Jurassic Series ; but the only two 

 recorded deep borings in and near Suffolk that have pierced 

 through the Cretaceous l<ase, at Culford on the north-west and at 

 Harwich on the south-east, show not a trace of anything Jurassic : 

 they pass suddenly from Cretaceous into far older rf>cks. And 

 here a paper that is to be brought before you must be anticipated, 

 to a slight extent, by adding that the trial-boring at Stutton 

 .•■hows just the same thing, the Gault resting directly on a much 

 older rock, which cannot l>c classed as of Secondary age. 



There is no need now to discuss the literature of the old rocks 

 underground in south-eastern England, that has often been 

 done. We may take the knowledge of what has been shown by 

 the various deep borings as common pro|)erty, and may use it 

 freely, without troubling lo state the source of each piece of in- 

 formation, and I will not therefore burden this address with 

 references. I had indeed thought of supplemcnling a former 

 account by noticing the later literature of the subject ; but 

 decided lo spare you from the infliction, and myself from the 

 trouble of inflicting ; though it may be convenient to add, in the 

 form of an Appendix, a list of the chief papers on the .subject that 

 have lieen published since the question was discus-sed at length 



in I*-*"' fticial memoir on the geology of Ix>ndon, and 



lo omissions in that work. Nor do I propose to 



mai , 111 criticism of |)a|icrs on the subject that have 



:ip(ic!irecl of late years : this is hardly the occasion for con- 

 troversy, which may well \k put off loa more convenient season. 

 Some general remarks, however, I shall have to make after pul- 

 ling the facts liefore you. 



There are ten deep lx>rings reaching lo old rocks in the 

 l^^pnilon Basin, of which accounts have been published. We 

 find 1I1..1 in r.,ur of ili, sc (.Mcux's, Slrealham, Richmond and 

 I^'' t.ilc those rocks from ihe Cretaceous 



tW'l i^ in which these la.st rest direct on old 



rock, IW.irc, Chu.liuiit, KentLsh Town, Crossness, Culford, and 

 Harwich). Slullonofcour.se makes a seventh. The Jurassic 

 rfjck.» occur only in Ihe southern lK)rings, cither in London or 



NO. 1 35 I, VOL. 52] 



still further southwanl, and in one case only (Dover) is there any 

 considerable thickness of these : in the other three they are 

 from 38.5 lo 87i feet thick. As far as regards -Suffolk and its 

 borders we may therefore disregard them, except in the far west, 

 near their outcrop, ami we may pass on to consider the older 

 rocks that have been fount!. 



So far ihc occurrence, next beneath the Cretaceous or Jurassic 

 beds, of Silurian, Devonian, and Carboniferous rocks has been 

 proved, whilst in some cases we are still doubtful as to the age 

 of the old rocks found. In live cases ilistinctive fossils have 

 been found (Ware, Chcshunt, Meux's, Dover, and Harwich), 

 but in live others they have not (Kentish Town. Crossness, 

 Richmond, Streatham, and Culford), and it is in the latter group 

 too that the character of the beds leaves their .age in doubt. So 

 far another must be added to these, as no fossil has yet been 

 found in the old rocks at Stutton. 



Of the above ten deep borings in the London Basin (using 

 that term in the widest sense, as including ihe Chalk tract that 

 everj-where surrounds the Tertiary beds) we owe nine to endea- 

 vours to get water from deep-sealed rocks, and in addition to 

 these nine wc have several other deep borings, which though not 

 carried through to the base of the .Secondary rocks, yet give us 

 much information concerning those beds (at llolkham, Norwich, 

 Combs, Winklield, London, Loughlon, Chatham, and Dover). 

 In one case only, that of Dover, h.as the work been done 

 for the purpose of exploration, but now, after a few years' 

 interval, a second trial has been made at Siulton. 



Now l)oth of these borings were started for a much more de- 

 finite object than merely to prove the depth to older rocks, or the 

 thickness of Ihe Cretaceous and Jurassic Series. There is one 

 |}articular division of those older rocks that has a distinct fas- 

 cination for others than geologists. We, hajipily, are content 

 to find anything and to increase our knowledge in any direction, 

 but naturally those who are not geologists, as well ;is many who 

 are, like to find something of immediate practical value, .^s 

 already shown, we owe much knowledge of the underground 

 extension of formations to explorations for water : il has now 

 become the turn of geologists to hel]) those who would like to 

 find that nmch less general, though nearly as needful and cer- 

 tainly more valuable thing, coal. 



The first |)lace lo suggest itself lo those geologists who had 

 worked at this question, as a good site for trial, was the neighliour- 

 hood of Dover, and for various gotxl reasons. Tile trial has 

 been made, and successfully, several hundred feel of Coal 

 Measures having been found, without reaching their base, but 

 with several beds of workable coal. 



Beyond that neighbourhood, however, geologists are not ia 

 such accord, and generally speaking, fairly good reasons caD 

 be given both for and against the selection of many tracts 

 for trial, except in and near London, where no geologists would 

 recomnienil il, from ihe evidence in *)ur hands. 



Let us then shortly review the evidence thai we have on the 

 underground extension of the older rocks in south-eastern 

 England, with a view of considering the question of the pos- 

 sibility of finding Coal Measures in any of the folds into tthich 

 those rocks have probably, nay almost certainly, been thrown. 



The area within which the borings that reach older rocks in 

 the London Basin is enclosed is an irregular pentagon, from near 

 Dover, on the south-east, to Richmond on the wesl, llicnce to 

 Ware, thence to Culford on Ihe north, thence lo llarHicli, .and 

 Ihence southward to Dover, the greatest distance between any 

 borings being from Dover to Culfor<l, ali.nit eighty-six miles. It 

 is therefore over a large tract, extending of course beyond the 

 boundaries sketched .above, thai we have good reason I o infer 

 that older rocks are within reasonable distance of the surface, 

 nowhere probably as much as 1600 feet, and mostly a good deal 

 less. 



We must now consi<ler some evidence outside the tract hilherto 

 dealt with. Southward of the central and eastern parts of the 

 London Basin we have eWdence that the Lower Cretaceous bed* 

 thicken greatly, from what is seen over their broad ouUrop 1)C- 

 tween the North and South Downs. We know also, from the 

 Dover and Chatham borings, that the Upper and Middle ij 

 Jurassic beds come in to ihe s<iulh-east, whilst the Siili-Wealdcn 11 

 Exploration, near Batlle, proves lliat those divisions Ihirkcn 

 greatly southward, Ihe laUer not having been bottomed al Ihe 

 depth of over 1900 feel, al Ihal Irial-boring. 



VVeslward, however, near Burford in Oxfordshire, and some 

 miles northward of ihe nearest pari of the London Basin, Car- 

 boniferous rocks have been found at the depth of aboul 1180 



