a Theory of the Earth'. 155 



17. To examine, in general, whether the ftrata exhibit 

 traces of violent convulfions, which may have changed 

 their primitive fituation ; or, on the contrary, whether the 

 Whole, as well as the {heightening of the ftrata, may be ex- 

 plained by fimple (inking down *. 



CHAP. XI. 



Observations to be made on Fiffures. 



1. Their form, dimenfions, breadth, extent, and direc- 

 tion. 



3,. Their fituation ; meafure of their inclination; direction 

 of that inclination in regard to the cardinal points, and in 

 regard to the adjacent mountain and valleys. 



4. To obferve, above all, the direction of fiffures in re- 

 gard to that of the planes of the ftrata ; becaufe fiffures, as 

 is prefumed, being produced, in general, by the earth fink- 

 ing down, and this finking clown being the effeft of preffure, 

 fiffures have been originally vertical or nearly fo ; and, on 

 the other hand, becaufe the ftrata having originally been 

 horizontal or nearly fo, the fituation of fiffures, in regard to 

 the ftrata, and the direction of both in regard to the horizon, 

 may give fome idea of the fituation which the ftrata had 

 when the fiffures were formed, and even of the changes of 

 fituation which the mountain afterwards experienced. 



Thus, fiffures perpendicular to the planes of the ftrata, in- 

 dicate that thefe fiffures were formed when the mountain was 

 ftill in its primitive fituation ; and if they are alio perpendi- 

 cular to the horizon, it proves that the mountain is ftill in 

 the fame fituation : but if fiffures perpendicular to the ftrata 

 are inclined to the horizon, we may conclude that the 

 mountain has changed its fituation fince. thefe fiffures were 

 formed f. 



• 18. To obferve, whether, on approaching the high primitive moun- 

 tains, the calcareous ftrata do not feem to have been revcrfed in a more vio- 

 lent manner. B. 



t An explanation and application of thefe principles may be feen in my. 

 Tr*vOs,§ 1048, 49, 5 o, and ui8. 



5. When 



