I865.J 59 [Lesley. 



All clefts in sandrocks must, as a general thing, remain 

 more or less open ; and they are the great channels of rapid 

 underground drainage. Fissures in shaly mudrocks are closed 

 as fast as made by the plasticity of the mass, and by the 

 perpetual percolation of fine clay into them. Those which 

 penetrate coal-beds, for instance, are almost all filled up with 

 clay from the overlying shales ; while many of the fissures in 

 the coarser sandrocks are only choked with loose sand or 

 small water-worn pebbles. All these are permanent reser- 

 voirs of salt water and oil. 



The law governing the number of these cleavage-planes is 

 a simple one ; the distance of the clefts from one another is, 

 in the main, proportionate to the massiveness of the strata 

 which they divide ; that is, the cleavage-planes of the great 

 beds of massive sandrocks lie much further asunder than those 

 of the thin-bedded sandstones ; while those subdividing beds 

 of shale are still closer to each other and more numerous. 



The law governing the size or width, and also the length 

 and depth of the fissures, is an analogous one : the great 

 sandrocks exhibit clefts sometimes many inches in width, 

 and running many yards or hundreds of feet continuously. 

 The pressure of these rocks sometimes carries their cracks 

 down (or up) through the softer and thinner beds, and the 

 strain of the dip will even cause these cracks to descend 

 many fathoms below where they originated. 



Some of the main fissures are known to be four inches 

 wide. Suppose them to be of all sizes, from four inches to a 

 quarter of an inch in width, and at various distance asunder, 

 from 5 to 50 feet, and to be limited to the sandrock itself, 

 say 30 feet in height; suppose we take the contents of the 

 fissures equal to s^o^h mass of the rock. Now, supposing 

 the oil to occupy but y'gth of the space in each fissure, the 

 rest being occupied by water and gas, we have a yield of oil 



of the Devonian Petroleum. It contains at least 200,000 tons of asphalt 

 (allowing it to go only 600 feet deep beneath the valley which it crosses) ; 

 able to yield by distillation 178 gallons of refined oil to the ton of 2400 

 lbs., and therefore over eleven millions of barrels of refined oil ; a quantity 

 which would allow a Noble and Delamater Well to spout 6000 barrels 

 per day for five years. 



