THE COAL QUESTIOV. 75 



surface the Lower coals will be found. Of course at this depth 

 they are quite unreachable, but toward the edge of the basin they 

 would probably rise, and where they are calculated to come 

 within four thousand feet of the surface they begin to figure 

 in the returns. 



So much for the method of estimating the supply which is 

 proved, or theoretically supposed to exist for us, in our Bristol 

 coal fields. 



The total thickness of the measures is about eight thousand 

 feet, that of the productive part being about five thousand feet. 

 There is an average of thirty-five seams of coal, with an aggregate 

 thickness of sixty feet. 



The length of the basin is twenty-six miles from the Mendips 

 to Cromhall Heath, and its greatest breadth is twelve miles, 

 viz., from Bristol to Twerton. The number of collieries working 

 is about forty-five. Many of the seams included by the Com- 

 missioners, who count all seams above a foot, are too thin to be 

 worked except at very shallow depths, and under favourable 

 conditions ; it will be necessary therefore to strike ofi" a certain 

 proportion of their gross estimates, — probably a twentieth of the 

 whole must be deducted for this reason. 



We may now turn to that part of the Eeport which deals with 

 the probability of finding coal undei the Permian, ]^ew Eed 

 Sandstone, or other superincumbent strata. This is drawn up 

 by Professor Eamsay, and the evidence is nearly entirely supplied 

 by the officers of the Geological Survey. Here again our interest 

 is excited by finding that Bristol figures in the list of probable 

 new coal-fields. The position of these "pastures new" for our 

 voracious engines, is along the banks of the Severn, from the 

 New Passage to near the mouth of the Avon. 



An anticlinal of Carboniferous Limestone and Millstone Grit 

 which rises to the surface, suggested so long ago as 1824 to 

 Buckland and Conybeare, the likelihood of the over-lying pro- 

 ductive measures being concealed in this district by the I^ewEed 

 Sandstone and surface deposits. In making the South Wales 



