68 REPORT — 1851. 



every step of deposition disturbed by drifting. Selecting from a variety of subjects 

 two cases of interest, tlie author described, above the middle of the red crag, a band 

 some feet in thickness which was traceable for half a mile on the Felixstow cliff, and 

 had in all that range apparently one direction of the inclination of its laminse, viz. to 

 the S.W. or nearly so, and in several parts of this range showed these laminae to be 

 curved, with the concavity upwards, the inclination of each lamina being greatest near 

 the surface (30°), and thence declining av.ay, so as, in the space of 30 or 40 yards, to 

 become horizontal. 



This result the author showed to be analogous to what happens in certain beaches of 

 modern date, and is in fact exemplified on the very beach which extends below the 

 crag, and is now spreading out continually further to sea. Another interesting cha- 

 racter of the mechanical condilions under which red crag was deposited, is found in the 

 position occupied by the separated pieces of bivalve shells. These (as first pointed out 

 by Mr. R. Johnson in the Proceedings of the Geological Society) were, when in a state 

 of tolerable completeness, very commonly found with their concave sides downwards, 

 a position which the observer alluded to conceived to be inconsistent with this arrange- 

 ment of water, and ascribed to currenti of wind. Professor Phillips showed, on the 

 contrary, by mechanical considerations, and by references to actual experiments, that 

 this was the very position which such shells must and do take up in finally settling to 

 rest from frequent agitation in water, such as happens on a sea beach ; and that no 

 other explanations ought to be admitted. Abundant proof of this was afforded by 

 trials with the crag shells and recent shells on the beach at Felixstow. In some places, 

 alternating with these inclined laminse, and defining them, were laminae of loam or 

 micaceous sands not shelly — evidently due to subsidence from muddy waters settling 

 to comparative quiet. Thus again intervals of agitation and comparative repose were 

 proved to have alternated, and this in a way to correspond with what is observed on 

 modern beaches. 



In regard to the conditions of land and sea during the accumidations of red crag, 

 the author stated in general terms his opinion that those deposits took place in a sort 

 of shallow bay, receiving matters from wasting cliffs and shifting shelly sands, by a 

 current varying in intensity, and subject to one or more specially tumultuous epochs. 



Lieut.-Colonel Portlock exhibited Fossils collected by Mr. R. Rubidge at Sunday 

 River, on the Cape frontier. They consisted of marine shells of the genera Ammo- 

 nites, Gryphcea, Pholadomya and Trigonia ; and plants of the genera Zamia, Neuro- 

 pteris, Pecopteris and Sphenopterls. The shells were apparently of Jurassic age ; the 

 plants had been examined by Dr. Harvey, and the species oi Neuroplerk, Pecopteris 

 and Sphenopferis, were regarded as chiefly resembling those of the coal of Australia, 

 ■whilst the presence of the genus Zamia in abundance impresses an oolitic aspect on 

 the flora. 



Explication cVu7i Tableau de V Etude Methodiqiie de la Terre et du Sol, 

 By M. Constant Prevost. 



Mr. Prestwicli, at the request of the President, explained that M. Prevost's object 

 ■was to introduce uniformity into geological nomenclature, and also to give a more 

 distinct meaning to scientific terms. At present each country had its own nomen- 

 clature, and many of the terms in use were invented at a time when the science was 

 one of imagination. M. Prevost had always advocated the view that causes now in 

 action were sufficient to account for all the phsenomena of the older rocks ; at the same 

 time he started with the supposition that the earth was originally in an extremely 

 heated condition. Round this heated globe a thin crust {sol) was formed, and gradu- 

 ally thickened by sedimentary deposits going on in all times, whilst volcanic outbreaks 

 ■were continually occurring from the interior. M. Prevost divided all the strata into 

 systems or series (terrains), representing periods of time, each necessarily including 

 marine, fluvio-marine, freshwater, terrestrial and volcanic deposits (formations). But 

 although the causes of each of these kinds of deposit must have been in operation 

 during every past epoch, it may be doubted whether we shall ever discover the equi- 

 valents — freshwater, terrestrial, volcanic, &c. — of every one of the known marine for- 

 mations. 



