Note f — BOOK III.
Reading edition
Id. ib. pag. 28. and 74. But Dr. Leigh in his Nat. History of Lancashire, speaking of the Coal-pits, denies the Strata to lie according to the Laws of Gravitation, saying the Strata are a Bed of Marle, afterwards Free-Stone, next Iron-Stone, then Coal, or Kennel-Mine, then some other Strata, and again Coal, &c.
But upon a stricter Enquiry into the Matter, finding I had reason to suspect that few, if any, actually had tried the Experiment, I was minded to bring the Thing to the Test of Experiment my self; and having an Opportunity, on April 11. 1712. I caused divers Places to be bored, laying the several Strata by themselves; which afterwards I weighed with all Strictness, first in Air, then in Water, taking Care that no Air-bubbles, &c. might obstruct the Accuracy of the Experiment. The Result was, that in my Yard, the Strata were gradually specifically heavier and heavier, the lower and lower they went; and the upper which was Clay, was considerably specifically lighter than the lower Stratum; which was first a loose Sand, then a Gravel. In which Stratum principally the Springs run that supply my Well.
But in my Fields, where three Places were bored (to no great Depth) I found below the upper (superficial Stratum) a deep Bed of Sand only, which was of different Colours and Consistence, which I weighed as before, together with the Virgin-Mould; but they were all of the same, or nearly the same specifick Gravity, both out of the same Hole, and out of different Holes, although the Sand was at last so gravelly, that it hinder’d our boring any deeper.
Upon this, fearing lest some Error might be in the former Experiments, I try’d them over again; and that with the same Success.
After this, I made some Experiments in some deep Chalk-Pits, with the Flints, Chalk, &c. above and below; but the Success was not so uniform as before.
Acquainting our justly renowned R. S. with these Experiments, they ordered their Operator to experiment the Strata of a Coal-Pit; the Success whereof may be seen in Philos. Trans. Nr. 336.