Mr. Penniston on the Induration of Chalk. 255 



of the masons, to make the bays of chalk, or rather of chalky 

 earth, which forms the banks adjoining the turnpike-road at 

 the bottom of Harnham Hill. 



The stream, as you are aware, at the upper side of this 

 bridge, runs extremely rapid, and I confess I had my doubts 

 whether this material would consolidate in so narrow a width 

 (not exceeding 2^- feet), and confined only between two hur- 

 dles (such as are commonly used for penning sheep), suffi- 

 ciently to resist the force of the river. 



In the progress of forming this bay, a considerable portion 

 of the finer particles of the earth washed away with the cur- 

 rent, but sufficient remained to answer every purpose intended. 

 It was formed by men treading in the earth ; and on the 

 evening of the day on which it was made, the whole substance 

 was like a bog, or quagmire, where pressure on any part ope- 

 rated on the whole bulk ; but on the following morning it was 

 a perfect wall : it continued for many weeks impervious to the 

 pressure of the stream, and when it was necessary to remove 

 it, it presented so obstinate a resistance, that several pickaxes 

 were broken in attempting to do so ; nor was it until the fol- 

 lowing summer, when the water was lower, that it was fully 

 cleared away, and then with the same labour and loss of iron 

 as before. 



The next proof I had of its utility, was at Burford Bridge 

 (a village just above Amesbury, Wilts). Here the pier of a 

 cast-iron bridge was literally underwashed, and in great part 

 destroyed, by the floods of 1823-4, and the bed of the river 

 so ploughed up, as to be in holes of from five to ten feet deep. 

 These, after restoring the piers, and repairing the bridge, I 

 filled up by driving piles, and ramming in between these piles 

 large rubble chalk, clay, and flints ; but in spite of the care I 

 took in the execution of that plan, the floods of the succeeding 

 winter cleared it completely out. A great portion of the lumps 

 of chalk were rolled some scores of yards down the stream. 

 The piles and clay vanished altogether. 



The specimens I had had of the chalk earth, induced me to 

 fill in these holes with the same kind of materials ; and I 

 employed some horses and carts to bring it from a chalk-pit at 

 some little distance, selecting such as had been pulverized by 

 wet and frost, and carefully discarding the larger lumps. 



