VOL. LXIV.] PHILOSOPHICAL TRANSACTIONS. 511 



raised, and consequently longer before they were covered with fresh incrustations, 

 these, from a long exposure to the air, would acquire a greater degree of 

 hardness. 



Whole houses in the neighbourhood are built of this stone, which they find 

 more durable than any other they meet with ; and as it has the excellent pro- 

 perty of growing harder, from being exposed, and has likewise many little cavities 

 and interstices, good mortar so insinuates itself into these, as to form a wall as 

 firm as one continued stone. This stratum affords curious and beautifully varied 

 petrifactions. Moss exhibits great varieties ; for it is evident, that the moss has 

 continued to vegetate, after the roots and lower parts had been penetrated by the 

 stony particles; and thus, stretching itself to a considerable extent, it has in 

 some places been mixed and interwoven with other substances. In some parts 

 snails have been arrested in their sluggish walks, and locked up in the stony 

 concrete. In others, the petrifying matter has shot, in different directions, and 

 formed an intricate kind of net-work. And in others again, there are large 

 masses, which on being broken asunder, are found hollow; and their cavities 

 ornamented with branches of petrifaction, somewhat resembling coral, but of a 

 darkish white colour, and generally of a rough and granulated surface. 



Under the stratum there is, from a foot to a foot and a half, of good soil ; 

 and immediately under this lies the limestone rock. The soil is of the same 

 nature with that of the adjoining fields, which form the slope of the hill, and is 

 evidently a continuation of that soil. Any further additions, to this petrified 

 stratum, are now inconsiderable, and in many places none at all ; for the two 

 principal springs are confined to their channels, covered from the day, through 

 the greatest part of their course, and are rapid in their motion. 



Had proper observations been made on the progress of this stratum, a tolerably 

 exact estimate might have been formed with respect to the time when these 

 waters were first impregnated with their mineral ingredients. From these 2 con- 

 siderations however, that the stratum is not very thick, and that the soil imme- 

 diately under it is a continuation of that which lies on the slope of the neigh- 

 bouring hills, it is probable that many centuries have not been requisite to its 

 production ; and consequently that these mineral waters arenot of very ancient date. 



And if we may rely on an observation, which he had from a plain, inquisitive, 

 and intelligent man on the spot, the source whence these waters derive their 

 impregnation, is in some degree exhausted. This person assured him, from his 

 own experience, that pieces of moss, and other substances, put in the course of 

 the waters, and in the same circumstances as formerly, require more than double 

 the time for their petrifaction that they did 30 years ago. The stratum there- 

 fore, from which the Matlock waters are impregnated, must either be consi- 



