SCJENCE-GOSSIP. 



GEOLOGY 



CONDUCTED BV EIIWARU A. MARTIN, F.G.S. 



Sections on the Brighion Line. — A geo- 

 loyiral section well worth visiting just now, is that 

 which has been exposed in cutting the new line from 

 Croydon to Red Hill, through the North Downs. 

 Where the line emerges from the new tunnel at 

 Mersthani, the deep cutting that has been made 

 can be viewed from the bridge which carries the road 

 from Merstham Church over the railway. At the 

 side of the road, riuming east and west, impure 

 sandstone layers may Ije obser\ed resting horizontally. 

 These as seen down the cutting, north and south, dip 

 at a considerable angle, and finally pass beneath the 

 chalk at the mouth of the tunnel. The material 

 quarried from the cutting has been carried south to 

 firm the embankment between Merstham and Red 

 Hill. In some places masses of Gault Clay, in others 

 Chalk have been thrown down, and on e.^posure to 

 xs'eathering, have split up into thin laminae. By this 

 means, blocks of tough chalk can be opened with biit 

 little assistance from the hannner, and occasional 

 fossils found. Nearer Red Hill, the Lower Greensand 

 series has been cut into, and the rise in the ground 

 which usually betokens the outcrop of these strata, is 

 here visible. The new rails will apparently be 

 carried through this formation in a short tunnel. 



Current Behdinc;. — There is much that can be 

 learnt in elucidation of geological problems by 

 watching the action of the sea as it eddies around 

 piles of piers or the ends of breakwaters at the sea- 

 side. The way in which the sand is carried down bv 



the stream, and the stream then passing on, felf 

 over the miniature fall made b)' the projecting 

 boss. Another result then showed itself. The force 

 of the fall cau.sed a pit to be excavated at its base, 

 which gradually deepened, and increased the amount 

 of the tall. As fresh material was brought down by the 

 stream, it was pushed over the .shallow edge of the trunk 

 of wood, and then slid down, at an angle of about 30 

 degrees, a declivity formed of ever-thickening strata. 

 Here, then, was an example of the manner in which 

 " current-bedding'' is formed. All the little stratula 

 of sand were pointing the .same way, that is, away 

 from the source of the current. They would all be 

 wedge-.shaped, the points of the wedges being deter- 

 mined down the declivity at the furthest point to 

 which the sand travelled at each fall. The sand was 

 prevented from accumulating, in the hollowed-out pit, 

 by the fall of the water. — Edward A. Martin. 



Striae as Evuience oe Ice-action.— The old 

 theory that striae upon rocks show, wiihout any other 

 support, evidence of ice-action, has received various 



little streams, ernerging fican pools that have been left 

 by the retiring tide, is pregnant with lessons to the 

 physical geologist. I remember watching such action 

 going on h\ the side of a groyne at Kemptown, 

 Brighton. The tide had retired, and the water, 

 which was still issuing from beneath the gravel on to 

 the wide stretch of sand, made a miniature river, and 

 hurried along the side of the groyne. At a certain 

 point it reached a huge boss of wood, that was 

 imbedded in the sand, and whose upper end was fixed 

 in the wooden gro\'ne by way of support thereto. 

 In passing round this huge trunk, the velocity of the 

 stream appeared to have been checked, perhaps in 

 the first place by the fact that the trunk projected above 

 the sand, and caused the energy of the stream to be 

 lost in car\ing a new and more sinuous passage 

 around it. The result .showed itself by a deposition 

 of the sand which had been held in suspension by 



shocks during recent years, and it is not now safe to 

 rely too much .upon such markings as proof of 

 glacier action. I have recently noticed similar mark- 

 ings on loo.se, wet .sand, after it has just been left by 

 the receding tide. Standing on the rocks facing a 

 sea-wall, and between two breakwaters, I noticed 

 that the sand stood very much higher against 

 the eastern groyne than against that to the 

 west of me. Each powerful wave that came in and 

 ascended the sand sw'ept over and across the shelving 

 bank, and returned to the sea in a direction almost at 

 right angles to that of its incoming. The result was 

 a series of fine groovings, like striae, and under 

 certain circumstances it can be imagined that these 

 might be rendered permanent. — .fi'flm'az'n' ^-/. Martin. 



A Plea eor Pieces.— It is not given to every 

 collector to obtain the best specimens. These, as a 

 rule, fall only to the hammer of the professional 

 geologist. Those who can only devote their Saturday 

 afternoons to study in the field, or are otherwise 

 limited in the time they can spend on the subject, 

 have frequently to be content with incomplete speci- 

 mens. Many practised geologists look .scornfully 

 upon such as these, but there is really a good deal to 

 be .said on their behalf When one considers the 

 building-up of reptiles and mammals which has 

 resulted from a few fragmentary bones, jaws and 

 teeth, or incomplete casts artificially obtained in the 

 case of the pliocene Lenham Beds : the leaf fragments 

 that have served in the cases of the Bovev Tracey 

 and the Bournemouth Beds, it is unwise to cast 

 aside the uns\'mmetrical and fragmentar}', because at 

 first sight they may appear to be valueless. There is, 

 besides, the advantage in testing the knowledge and 

 acumen of the student by these, when complete 

 specimens would present no difliculty. 



