openings, thus carrying off the waters by four outlets. All these 

 four cataracts of Velinus, Mercatus describes* as much narrower 

 than when first opened, and alarming the Reatines, lest the increas- 

 ing stone should cause the lake to extend its bounds, and destroy 

 their charming country. 



Nor is their overflow the only inconvenience which waters, pos- 

 sessing this property, occasion to those who live in their neigh- 

 bourhood ; since the continual deposition, and increase of stony 

 matter, in evqry crevice, and in all loose soil, in which they pene- 

 trate, and on every spot on which they rest, is also a source of dis- 

 . appointment ; those parts being thus rendered stony and barren, 

 which had perhaps been allotted to corn and pasturage. Thus the 

 passage of the water having been interrupted in the subterranean 

 passages of the Claudian aqueduct of Rome, the water, soaking into 

 the bibulous earth, and penetrating into the surrounding cavities, 

 formed an extensive quarry of this tufaceous stone -f. At Matlock, 

 is a remarkable stratum of this kind, which, according to the ac- 

 count given by Dr. Dobson, in 1774 1, was 500 yards in length, in 

 several places ; nearly 100 yards in width; and, in the thickest parts, 

 from three to four yards in depth. The manner in which this great 

 body of stone had been produced, Dr. Dobson remarks, is easily 

 ascertained. Within the memory, he says, of some persons now 

 alive, the waters of Matlock were not appropriated to the purposes 

 either of bathing, or of drinking. They issued from near the bottom 

 of the hill, which lies to the west, immediately behind the present 

 houses, and ran, at random, down a declivity of about 100 yards, 

 to the river Derwent. In their course they formed large petrified 

 masses, intermingled with great quantities of petrified moss, nuts, 

 leaves, acorns, pieces of wood, and even trunks of trees. This 



* Metallotheca Vaticana, p. 252. 



t Roma Vetus ac Recens, &c. Auctore Alexandro Donate, p. 400, 1725. 



$ Philosophical Transactions, vol. Ixiv. 



