7HEORT of the EARTH. 259 



cooling, they muft have formed rents or reparations of their 

 fubftance, by the unequal degrees of contraction which the 

 contiguous ftrata may have fuffered. Here is a moft decifive 

 mark by which the prefent queftion muft be determined. 



THERE is not in nature any appearance more diftincl than 

 this of the perpendicular fiflures and feparations in ftrata. 

 Thefe are generally known to workmen by the terms of veins 

 or backs and cutters ; and there is no confolidated ftratum that 

 wants thefe appearances. Here is, therefore, a clear decifion of 

 the queftion, Whether it has been by means of heat, or by 

 means of aqueous folution, that collections of loofe bodies at 

 the bottom of the fea have been confolidated into the hardeft 

 rocks and moft perfedl marbles. 



ERROR never can be confiftent, nor can truth fail of having 

 fupport from the accurate examination of every circumftance. 

 It is not enough to have found appearances decifive of the que- 

 ftion, with regard to the two fuppofitions which have been now 

 confidered, we may farther feek confirmation of that fuppofi- 

 tion which has been found alone confiftent with appearances. 



IF it be by means of heat and fufion that ftrata have been 

 confolidated, then, in proportion to the degree of confolidation 

 they have undergone from their original ftate, they fhould, c<z- 

 teris paribitS) abound more with feparations in their mafs. But 

 this conclufion is found confiftent with appearances. A ftratum 

 of porous fand-ftone does not abound fo much with veins and 

 cutters as a fimilar ftratum of marble, or even a fimilar ftratum 

 of fand-ftone that is more confolidated. In proportion, there- 

 fore, as ftrata have been confolidated, they are in general inter- 

 fecled with veins and cutters ; and in proportion as ftrata are 

 deep in their perpendicular fedlion, the veins are wide, and 

 placed at greater diftances. In like manner, when ftrata are thin, 

 the veins are many, but proportionally narrow. 



IT is thus, upon chemical principles, to be demonftrated, 

 That all the folid ftrata of the globe have been condenfed by 



K k 2 means 



