HARDWICKE'S SCIENCE-GOSSIP. 



251 



group of fruits of a golden-yellow hue. The circum- 

 stance is note-worthy, inasmuch as it proved to be 

 a rare species of which the Plasmodium stage was 

 previously unknown to scientists. 



Yet another instance of the peculiar habits of these 

 organisms. Two small masses of Plasmodium had 

 been under observation for several weeks, and it was 

 thought they did not seem healthy, possibly wanting 

 a change of diet. Accordingly a fungus, one of the 

 polyporous group, was soaked in water, divided in 

 halves, and a portion placed near each. Both of the 

 Plasmodia crept from their positions, and crawled 

 over the respective portions of supposed aliment. 

 Tj nfortunately it was the last joumey for each of 

 them, for either from the detrimental qualities of the 

 fungus, or from acarites that may have infested them, 

 both plasmodia perished, after two or three days of 

 evident decadence. 



Jas. Saunders. 



Luton. 



( To be continued.') 



OX THE UNDERGROUND GEOLOGY OF 

 LONDON. 



By Edward A. Martin, 

 Author of "Glimpses into Nature's Secrets," etc. 



THERE are few subjects of geological interest 

 which have a greater fascination for the 

 theorising student, than the subject of the position 

 which the various geological strata have, and the 

 directions which they take, under our great metro- 

 polis. 



Almost all the information which we possess as to 

 the bearings of these underground strata, have been 

 obtained from borings which have been made in 

 search of water. Thus, when the object of the boring 

 has been achieved, or when on the other hand its 

 failure has become an established fact, the prosecu- 

 tion of the work has been stopped, and the geologist 

 has been left to wander in the field of speculation as 

 to what kind of strata would next have been met 

 with deeper down. 



We have then a limited number of borings, from 

 whose data we are able to speculate, and from these 

 we are able to form a general opinion, although not 

 a very definite one, as to the contour of the under- 

 ground palaeozoic land-surface, which has been 

 shown to' exist by such geologists as De la Beche, 

 Godwin-Austen, and Prestwich. 



To get a clear understanding of the depths in the 

 borings at which various strata have been met, and 

 of the superficial distance at which the sites of the 

 borings stand in relation to one another, the accom- 

 panying diagrams have been prepared which may 

 perhaps help to attain this object, and in view of 

 discoveries which have been made of coal in our 

 south-eastern counties, and of possible results which 

 may be obtained in connection with, borings now 



in course of being carried out, it is necessary that 

 the knowledge already obtained should be under- 

 stood. 



The positions of certain of the borings appear to 

 stand in relation to one another in general northerly 

 and southerly direction. Commencing beyond the 

 northern limits of the metropolis, at the boring made 

 at Ware, in Herts, and pursuing a southerly direction, 

 we come to that made at Turnford, after which 

 follow those at Kentish Town, Tottenham Court 

 Road (Meux's), Streatham, and the Caterham 

 Waterworks. From these we have data from six 

 borings, all more or less in a line north and south of 

 one another. 



At Ware the base of the chalk was met with at 

 a depth of 55S ft., at Turnford 784 ft.,. at Kentish 

 Town 969J ft., at Meux's 814ft., at Streatham 864ft. 

 and at Caterham Works, at 45S ft. The upper 

 greensand and gault clay were met with regularly 

 throughout the whole distance, although each of 

 these slightly thinned immediately under central 

 London. So far no difficulty was encountered in 

 deducing the underground contour of the strata from 

 the facts furnished. But beneath the gault, the strata 

 met with were as varied as they could well be. 



One of the most recent surprises was the discovery 

 of the complete thinning out of the lower green- 

 sand beds beneath London. At Ware, on the north, 

 these beds had already almost disappeared, there 

 remaining but a foot of strata, which have been 

 doubtfully classed as belonging to this series. On 

 the south, when the Southwark and Vauxhall Water 

 Company made their boring at Streatham, in order 

 to tap the supply of lower greensand water at that 

 place, it was discovered that these strata had ceased 

 to exist, and that they had already completely thinned 

 out at some point between Streatham and the es- 

 carpment of the North Downs. These two facts 

 therefore enable us to construct our diagram so far 

 with certainty. 



One leading fact stands out in connection with 

 the boring at Ware, which gives us there a secure 

 footing from which to start our deductions as regards 

 the more ancient rocks. Strata which were unmis- 

 takably recognisable as of Silurian age were there 

 met with at a depth of 796 ft. Now, since at Turnford, 

 only eight miles south, beds of cretaceous age con- 

 tinued as deep as 98oJft., it was evident that between 

 these two places there must have been a very sudden 

 dip in the strata, in order to allow of comparatively 

 recent beds to be met with nearly two hundred feet 

 deeper at the latter place, than the older beds at the 

 former place. The dip too must be greater than this 

 alone would imply, for although no Devonian beds 

 were found above the Silurians at Ware, these 

 actually appear at Turnford, immediately beneath 

 the gault clay (cretaceous). The boring was only 

 carried 29J ft. into the Devonian rocks, so that we 

 are at present in the dark as to the depth at which 



