138 Corresipondence, 



venture, perhaps, to solicit space for an account of some curious 

 circumstances given in tM^o papers in the fourth, volume. 



The first paper is by J. W. Colenso, Esq.^ (read October, 1829), 

 entitled "A description of Hajjpy - Union Tin Stream Work at 

 Pentuan."^ The valley of Pentuan is near St. Austell, and is de- 

 scribed as about six hundred feet in breadth, but narrowing in 

 places to three hundred, or even one hundred, the surface having a 

 fall of one hundred and twenty feet in four miles. The rock is blue 

 slate, covered in the bottom of the valley by an alluvial deposit, 

 ■which, commencing at St. Austell bridge, becomes about sixty feet 

 deep at Pentuan. The section of this alluvium at Pentuan is said 

 to be the following (descending order) :— 



g. Eiver and sea sand, silt, etc ., 20ft. 



Under this, at one place, just on a level with present 

 low water at spring tides, piles were found as if for the 

 construction of a foot-bridge. 



/. A stratum of sea sand, with timber trees, chiefly oaks, 

 lying in all directions, and also the remains of red-deer, 

 heads of oxen, with the horns tmming down, different 

 from any now in Britain, said to be like those at the 

 Cape of Good Hope ; the bones of a large whale, and 

 human sJculIs, supposed to he eitlier African or Asiatic ... 20ft. 



e. Silt, in the middle of which is a layer of stones, conglo- '^ 



merations of sand and silt, with sometimes wood and 

 bone 2ft. 



d. Sea sand with shells, the water proceeding from which 



is salt, while that above and below is fresh 4in. 



€. Silt or " sludge," brown or lead-coloured, with shells, , 

 wood, hazle-nuts, bones of deer, oxen, etc. ; the bivalve 

 shells in layers, valves often united, spolcen of as sea- 

 shells. There was one piece of oak that had been 

 "brought into form by the hand of man," but had 

 floated in the sea, as a small barnacle was fixed at 

 one end 10ft. 



h. Dark silt mixed with decomposed vegetable matter, 

 having at top a layer of moss scarcely altered " almost 

 retaining its natural colour," with leaves of trees, 

 hazle-nuts, and sticks, 30 feet below level of sea at 

 low water, 48 below high tides ; extends with some 

 interruj)tion all over valley 2ft. 



a. The tin ground, sand and clajr, with fragments of granite, 

 elvan, greenstone, ^'killas" or clay slate, and iVesforae, 

 a hard black rock, and vein stones, with sand and 

 pebbles of tin-ore, the tin mostly at bottom, varying 

 from 3 to 6 and 10ft. 



This paper is followed by papers on the stream tin- works, by Mr. 



1 "Was this gentleman the father of my old college friend and companion, the 

 Bishop of Natal ? 



2 See De la Beche's Eeport on the Geology of Cornwall and Devon, 1839, p. 406. 



