IS 15.] An Essay on Rents. 277" 



When we see these tabular masses lying in a rent of the coal 

 formation, between the surfaces of separation of the strata on the 

 sides of that rent whose matter is the same as theirs; when in 

 addition we recollect, as before stated, that these masses in granitic 

 rents are granite, &c. we are irresistibly led to the conclusion that 

 these masses arc a part of the matter which existed in tlie forma- 

 tions before these rents took place ; because had they proceeded 

 either from above or below, they could not have assumed their 

 present " h'lghli/ inclined positions ; " nor is it probable that they 

 would be similar to the matter near the rents ; and it is still less 

 proljable that where the matter of a formation consists of strata of 

 different denominations, these masses would lie close to strata 

 whose denominations are similar to theirs. These remarks are 

 sufficiently conclusive : but there is one fact still which gives them 

 greater weight, and that is, that parts of the coal from which these 

 masses are supposed to proceed, are wanting to such distances from 

 these rents, that the area of tiie parts wanted is about equal to that 

 of the large masses in the rents. Therefore I think the position, 

 that the matter thus arranged in rents proceeds from the matter 

 which is contiguous to them, is fully proved. 



The process by which these masses have acquired their present 

 situations and positions may have been similar to that which is 

 described as follows. After the formation of the separated surfaces 

 of the stratum in which the lowest extremity of a rent is situated, 

 the parts of that stratum which were still in a fluid state passed 

 naturally into the rent, or were forced into it by the incumbent 

 ■weight as the rent gradually increased in width. Several parts of 

 the strata close to the rent would be fluid, therefore near the wiiole 

 of it was filled opposite these parts ; in other parts only small por- 

 tions of the strata were fluid, of course only small parts entered the 

 rent ; and in other parts the strata were sufficiently solid to resist the 

 weight of the incumbent matter, so that from these parts no matter 

 was forced into the rent. It is easy to conceive that such a modifi- 

 cation ill the arrangement of the masses as that already described 

 would take place in this manner. From the angular position of the 

 masses in a bended-tabular rent, and from the other phenomena 

 already described respecting them, 1 deduce the formation of the 

 lent in the stratum opposite its lowest extremity so long before its 

 conmiencemcnt in tiie second stratuni as to allow the matter which 

 entered the rent from the lowest stratum to be so much conso- 

 lidated, that it would retain its position as the rent continued to 

 widen, and would support the fluid matter which rested on it when 

 the formation of the rent in the second stratum from the bottom 

 commenced ; and tlie commencement of the rent's formation in 

 every stratum, reckoning upwards, before its commencement in 

 that stratum which rests on it, such a length of time as 1 have 

 mentioned to take place between the commencement of the rent's 

 formation in the lowest stratum, and of its commencement in that 

 hlratum which lies on it. 

 G 



