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HARD WICKE' S SCIENCE-GOSSIP. 



history, and source of origin, of the materials which 

 compose the secondary deposits of this country. The 

 pebbles, as a mass, have been derived from altered 

 sedimentary strata, such as shales converted into 

 flinty slates, or hornstone, and which must also have 

 contained great subordinate veins of quartz-rock ; 

 water-worn crystals of felspar may also be detected, 

 indicating the loose structure of the mass of felspathic 

 granite or porphyry, from which they were sepa- 

 rated'" ("Quart. Journ. Geol. Soc," vol. vi. p. 

 458). I make no apologies for the above, firstly, 

 because it gives a more comprehensive view of the 

 subject than anything I am likely to indite, and, 

 secondly, because the volume is probably not acces- 

 sible to most of the readers of Science-Gossip. A 

 little farther on, Mr. Austin says: "If sections be 

 taken at intervals within the Wealden area, as from 

 Farnham to Maidstone, an insight will be got as to 

 the change which the beds of the lower greensand 

 undergo from south to north, and it will then be seen 

 that the subordinate shingle-bands became coarser 

 northwards, so that at the latter place rounded blocks 

 of granite have been met with nearly a foot in 

 diameter. Such a fact as this is of itself sufficient to 

 indicate the direction in which the coast-line of the 

 lower greensand lay." 



After the above quotations a few observations on 

 the pebbles themselves may not be out of place. 

 The black flinty pebbles so abundant in the Bargate 

 pebble-bed are usually sub-angular in form, but ap- 

 pear to have undergone a vast amount of wear. They 

 are derived from the harder bands of old rocks such 

 as occur in the West of England. Some I obtained 

 from Littleton appear still to retain their slaty 

 cleavage, as if their metamorphosis had not been 

 quite complete. The brown flint pebbles seem 

 similar, excepting in colour. The quartz of the 

 Bargate pebble-bed is very much worn, but in some 

 of our ironsands I have found exceedingly sharp 

 fragments. Quartzite pebbles are rare. Agate and 

 jaspar occur, but are rare ; but it must be borne in 

 mind that these terms are not strictly accurate. 

 There are also a few fragments of hard flinty rocks, 

 which are scarcely at all water-worn. In the event 

 of pebbles of the lower greensand being recognised 

 as older than the rocks which have been reached 

 north of London, namely, silurian, the question arises, 

 Are we to suppose that the rocks formed part of the 

 coast of the greensand sea, or were they derived from 

 .some older pebble-bed ? The silurian rocks them- 

 selves abound in pebble-beds and conglomerates, not 

 to mention abundance of pebbles in beds of younger 

 strata. I am sometimes disposed to take the latter 

 view, seeing that the pebbles occurring in the fresh- 

 water beds of the Wealden are also palaeozoic. Now 

 the Wealden is an estuarine deposit throughout, and 

 it is generally admitted that river action alone is 

 inadequate to reduce such hard material as those in 

 question to pebbles. I take them, therefore, to have 



been brought down into the estuary by rivers from 

 old marine pebble-beds existing on the ancient conti- 

 nent. Thus, in the flint-gravels of our modern rivers 

 no flint-pebbles occur, except such as have been 

 derived from the lower tertiary. Besides the pebbles 

 and rock fragments there are a few rust-flakes, 

 bronzy-flakes, and nodules, as also minute iron-cists, 

 but these are of no particular interest, they may have 

 come from almost any bed, the lower beds of the 

 greensand not excepted. Very probably they are of the 

 same age as the ironstone casts, such as the ammo- 

 nites, Lamberti, from the Oxford clay. Besides the 

 pebbles of the Bargate, there is, in some localities, 

 as at Great Tangley, near Chilworth, a collection Of 

 pebbles quite at the top of the Hythe beds.* There 

 is a pit near Chilworth, or rather a sand-hole close to 

 the tail of the "y" in "Great Tangley" on the 

 one-inch map of the Geological Survey. The pebbles 

 here are dispersed throughout the sand-beds and are 

 not in regular seams. Many of them are exceedingly 

 shiny, which is probably owing to their extreme 

 hardness, those which have been exposed to the wash 

 of the rain in the runnels are especially shiny. A 

 friend has cut open one of the shiny black pebbles : it 

 is red inside and seems like an agate. Here I may 

 remark, that although most of our pebbles appear to 

 be water-worn fragments torn from some larger 

 mass, there are a few which have a nucleus differing 

 in colour and even in texture from the exterior. 

 These may probably have been formed in the cavities 

 of igneous rocks. Turning to the west of Godalming, 

 there is a sand-hole at the corner of Shackelford 

 Heath, close to the junction of the Folkestone and 

 Hythe beds. Here I found a large pebble of 

 saccharine quartz. The sand of this pit is somewhat 

 similar to that of Tangley pit. There are small 

 angular fragments of quartz. 



Turning, now, to the Farnham and Crooksburg 

 district, palzeozoic pebbles occur wherever the turf is 

 broken for digging ironstone, as between Hankley 

 Hill and Yagden Hill, near Stockbridge Pond. 

 There has been a large quantity of ironstone (the 

 Carstone beds) dug on Charles Hill. In it I found 

 large quartz and quartzite pebbles ; one, a large 

 pebble (probably of quartzite), weighing twelve 

 ounces. I have received palaeozoic pebbles from 

 Frensham, Great and Little Ponds, Tancredsford 

 Common, and Churchers Hill. A friend remarks on 

 a selection of pebbles (mostly from Charles Hill), that 

 they are from the old palaeozoic series, of which we 

 have an exposure at the surface along the Franco- 

 Belgian range, and as near to us as the Boulonnais 

 district. They are mostly, if not all, from the 

 silurian and even lower series, with great quartz 

 veins. It is 'possible that these pebbles above the 

 Bargate may have been derived from older rocks 



* I use Mr. Topley's divisions, and include the Bargate 

 with the Hythe beds. 



