TRANSACTIONS OF THE SECTIONS. J5 



drum, which docs not differ much from that indicated by the vessel of water, and 

 take the distance at thirty-seven miles, we obtain a velocity of propagation of 470 

 feet per second; and if we take the latest result at Quilon, or 4 h 19 m , we have still 

 a velocity of only 530 feet per second — little more than three-fifths of that found 

 by Mr. Mallet in wet sand. If we take the W.N.W. as the direction of propaga- 

 tion of the shock, or any other than that direct from Quilon, the velocity will of 

 course be diminished. It should be remarked that the laterite, which forms the 

 upper stratum (about 30 feet deep) between Quilon and Trevandrum, is a clayey 

 rock, in a semi-pasty condition of perhaps the lowest degree of elasticity ; and the 

 laterite reposes in some places on strata of sand and clays. 



On the Course of the Thames from Lechlade to Windsor, as ruled by the 

 Geological Formations over which it passes. By the Rev. J. C. Clutter- 

 buck, 31. A. 



The tortuous course of the Thames between Lechlade and Windsor shows that 

 there must be some physical cause which obliges it to deviate from the straight line 

 it would naturally take to its outfall. This is l'ound in the obstructions encountered 

 in its passage over or through the various strata. From Lechlade to Sandford the 

 river finds its bed in the Oxford clay ; it then passes through a narrow gap in the 

 middle oolite to the Kimmeridge clay, holds its course on that clay, under the 

 escarpment of the Iron-sand in Nuneham Park, turns the escarpment at Culham, 

 passes to the Gault at Appleford, touches a ledge of the Iron-sand at Clifton Hamp- 

 den, returns to the Gault, enters the Greensand near its junction with the Thame 

 stream, passes to the Chalk, in which it finds its bed to the point, — which is the limit 

 proposed for consideration. The natural obstructions are found at the junction of the 

 different strata. The quantity of water flowing down the river, whether issuing in 

 perennial springs, or thrown from the surface in flood, is due to the geological condi- 

 tion of the district. The tributaries or feeders discharge more or less of perennial or 

 flood water, as they carry the water from permeable or impermeable strata. The 

 flooding of the district necessarily affects the sanitary condition of Oxford. The city 

 itself is placed on a bed of gravel, overlying the Oxford clay, the surface of which 

 undulates so that the water is stanked back in the gravel ; it was cutting through one 

 of these undulations, in carrying out the Jericho drainage, that deprived many wells 

 in Oxford of their water. As this bed of gravel extends beyond the limits of the city, 

 on the subsidence of the floods, the water filtrates through the gravel, and thus 

 noxious evaporation is diminished. Considerable accumulations have raised the bed 

 of the river in many places, evidence as to the date of which is found in antiquities 

 which have been discovered when constructing locks or weirs, or in dredging for gravel. 

 At Sandford, arms of the time of Charles I. have been found 8 feet below the river- 

 bed, relics of greater antiquity and at various depths have often been found in other 

 places, where the bed of the river has been raised, or, as in some cases, entirely 

 changed its course. The phenomenon of the formation of ice at the bottom of the 

 stream, when the temperature falls to 20 Fahr., and the transportation of stones from 

 the bottom by the ice rising to the surface, adds to the natural obstructions in the 

 stream, and hinders the passage of the flood-waters by which so much damage has 

 been done at various times in the neighbourhood of Oxford. The paper, which 

 entered into full details, was illustrated with a map, sections, and diagrams. 



Photographs of a Paddle of PUosaurus of great size, found at Kimmeridge, were 

 exhibited by Mr. R. Damon, of Weymouth. 



Remarks on the Elevation Theory of Volcanos. 

 By Professor Daubeny, M.D., F.R.S. 



This paper was chiefly intended as a protest against the assumption of certain geo- 

 logists, that because it had been shown, more especially by Sir Charles Lyell in his 

 memoir published in the ' Philosophical Transactions ' for 1858, that sheets of compact 

 lava have been formed on steep inclines, it therefore followed, that all volcanic moun- 

 tains have been built up by a series of successive eruptions. 



Not denying that this explanation may serve for the oldest, as it certainly does for 

 the more recent beds, which constitute such mountains as Etna and Vesuvius, the 



