Effects cf Heat inodified by Compression. 209 



peated efforts, succeeding each other from below, would at 

 last elevate the strata into their present situation. 



The Huttonian theory embraces so wide a field, and com- 

 prehends the laws of so many powerful agents exerting their 

 influence in circumstances and in combinations hitherto un- 

 tried, that many of its branches must still remain in an un- 

 finished state, and may long be exposed to partial and plau- 

 sible objections, after we are satisfied with regard to its fun- 

 damental doctrines. In the mean time I trust that the ob- 

 ject of our pursuit has been accomplished, in a satisfactory 

 manner, by the fusion of limestone under pressure. This 

 single result affords, I conceive, a strong presumption in 

 favour of the solution which Dr. Hutton has advanced of 

 all the geological phaenomena ; for the truth of the most 

 doubtful principle which he has assumed, has thus been 

 established by direct experiment. 



APPENDIX. 



No. I. 

 Specific Gravity of some of the foregoing Results. 



As many of the artificial limestones and marbles produced 

 in these experiments were possessed of great hardness and 

 compactness, and as they had visibly undergone a great di- 

 minution of bulk, and felt heavy in the hand, it seemed to 

 me an object of some consequence to ascertain their specific 

 gravity, compared with each other, and with the original 

 substances from which they were formed. As the original 

 was commonly a mass of chalk in the lump, which, on 

 being plunged into water, begins to absorb it rapidly, and 

 continues to do so during a long time, so as to vary the 

 weight at every instant, it was impossible, till the absorp- 

 tion was complete, to obtain any certain result ; and to allow 

 for the weight thus gained, required the application of a 

 method different from that usually employed in estimating 

 specific gravity. 



Vol. 25. No. 99. Aug. 1606. O In 



