840 



COAL 



beneath the Permian and other newer strata at depths exceeding 4,000 foot is com- 

 puted at upwards of 41,144,000,000, as appears by the following Table : 



Estimate of Quantities of Coal at Depths over 4,000 /<** beneath the Permian, 

 New Bed, and other Strata. 



Of this quantity it will be seen that more than 29,000,000,000 of tons are assumed 

 to lie at depths of between 4,000 and 6,000 feet, at which latter depth the tempera- 

 ture of the earth, it is supposed, would be 150 F. The remainder, amounting 

 to more than 15,000,000,000 of tons, is assumed to lie at depths varying between 

 6,000 and 10,000 feet, at which maximum depth the temperature of the earth, 

 according to the prevailing views, would be 215 F., or three degrees above the 

 temperature of boiling water at the sea level. To these quantities are to be added 

 7,320,000,000 of tons returned as being at greater depths than 4,000 feet within the 

 area of the known coal-fields. Of this quantity probably 5,922,000,000 of tons lie 

 between the limits of 4,000 and 6,000 feet in depth, and the remaining 1,397,000,000 

 of tons between 6,000 and 10,000 feet. 



With these additions the total quantity of coal lying at depths exceeding 4,000 feet 

 will be a little more than 48,465,000,000 of tons. 



It is entirely a matter of conjecture whether any or what portion of this coal can 

 ever be worked ; but if wo were to suppose the whole to become available, we should 

 have to make the following corrections in the number of years' duration given above 

 as the result of the different modes of viewing the question : 



1st. The 360 years would be altered to 433 years. 



2nd. The 276 years based on an increasing consumption in arithmetical ratio would 

 be altered to 324 years. 



3rd. The 1,273 years computed on the supposition of non-increasing consumption 

 would be altered to 1,695 years. 



Whatever view may be taken of the question of duration of coal, the results will be 

 subject to contingencies, which cannot in any degree be foreseen. On the one hand, the 

 rate of consumption may be thrown back to any extent by adverse causes affecting 

 our national prosperity ; and on the other hand, new discoveries and developments in 

 now directions may arise to produce a contrary effect upon the consumption of coal. 

 Every hypothesis must bo speculative, but it is certain that if the present rate of in- 

 crease in the consumption of coal be indefinitely continued, even in an approximate 

 degree, the progress towards the exhaustion of our coal will be very rapid. 



The numbers given in the preceding Table (p. 838) are sufficiently consistent with 

 each other to represent the changes which have taken place over a period of years. 



We find the following differences in the number of the collieries in 1858 and 1868 : 



1858 1868 



England 2,090 2,268 



Wales 360 364 



Scotland 417 433 



Ireland 40 40 



Total 



2,907 



3,105 



The increase being 198 collieries in the ten years. In 1872 the number of collieries 

 returned were 3,001. 

 With the view of showing at a glance the condition of our coal trade, the produc-. 



