1865,] FOSTER AND lOPLET DENUDATION OP THE WEALD. 461 



Mr. Martin *, in a series of publications extending over thirty- 

 years, taught that the Weald was denuded " by the joint operation 

 of earthquakes and diluvial currents." The results of these violent 

 actions he found in the various " drifts " with which the country is 

 in places covered. 



Mr. Hopkins t, in 1841, submitted a paper to the Society, " On 

 the Structure of the Weald," in which some of the chief Hnes of 

 disturbance were traced, and their supposed bearing on the physical 

 geography of the Weald pointed out; also the connexion between 

 transverse and longitudinal fractures. We shall allude more fully 

 to this subject immediately. 



Sir Charles Lyell J, in 1833, brought forward the marine theory 

 of denudation, which, with little alteration, has held its place until 

 the present time. 



Sir Eoderick Murchison §, in 1851, published his paper " On the 

 Flint Drift of the south-east of England." He described with great 

 care the drift of the Wealden area generally, and considered it to be 

 owing to great rushes of water which mingled the debris of the 

 various beds into the present drift deposits, burying the remains of 

 Mammalia. This took place when " the country had to a large 

 extent assumed its present form." 



Col. Greenwood ||, in 1857, published his views upon the question 

 of denudation with special reference to the Weald. He maintained 

 that the valleys were wholly formed by " rain and rivers." 



In 1862 Mr. Jukes ^ read before the Society a paper on the river- 

 valleys of the South of Ireland, in which he advocated the theory 

 that these valleys were formed by atmospheric denudation. In a 

 postscript (p. 400) he adds, " My acquaintance with the Weald of 

 Kent is too superficial to allow me to express an opinion ; but per- 

 haps I may venture to ask the question, whether the Chalk, 

 when once bared by marine denudation, which perhaps removed it 

 entirely from the centre of the district, has not been largely dis- 

 solved by atmospheric action ; and whether the lateral river- valleys 

 that now escape through ravines traversing the ruined walls of 

 Chalk that surround the Weald may not be the expression of the 

 former river- valleys that began to run down the slopes of the Chalk 

 from the then- dominant ridge that first appeared as dry land 

 during or after the Eocene period?" 



Prof. Eamsay, in 1863, while admitting that considerable ma- 



* ' Geological Memoir on Western Sussex,' 1828 ; Phil. Mag. (1829), p. Ill ; 

 Pliil. Mag. 4th series, vol. ii. 1851 (pp.44 et seq.), containing a paper read before 

 the Geol. Soc. in 1840; Phil. Mag. (1854), p. 166; Pliil. Mag. (1856), p. 447; 

 Quart. Journ. Geol. Soc. vol. xii. (185G), p. 134. 



t Trans. Geol. Soc. 2nd series, vol. vii. (1845) (read in 1841). 



X ' Principles of Geology,' 1st edit. vol. iii. (1833), chap. 21. 



§ Quart. Journ. Geol. Soc. vol. vii. p. 349. 



II ' Rain and Eivers ; or Plutton and Playfair against Lyell and all Coiners,' 

 18.57. 



1[ Quart. Journ. Geol. Soc. vol. xviii. (1862), p. 378. See also a letter by Mr. 

 Jukes, in ' The Reader ' for 12th March 1864. 



VOL. XXI. — PART I. - 1 



