68 



the store in the entire coal-field to be nearly 7,000,000,000 of 

 tons, and the known yield at 1,000,000 tons per annum, 

 there is sufficient coal to last nearly 6,000 years, or, taking the 

 quantity known to the depth of 4,000 feet, which is 4,219,000,000 

 of tons, the period of duration at the same rate of yield may be 

 computed at 4,000 years. 



Looking, therefore, at the supply thus measured, as based 

 tipon known quantity, rate of extraction, and depth to which in 

 future coal may be won, it is convenient, according to the 

 Royal Commission, to divide the coal-measures of the basin into 

 zones of depth, and then estimate for extraction and distribution; 

 bearing in mind, however, that below the zone of 3,000 feet the 

 ingenuity of man must be taxed to the utmost to realize those 

 yet deeper seated stores of coal. The zones of depth assigned 

 by the Royal Commission give the following assumed and 

 approximate quantities of coal contained in them. : — 



At a depth not exceeding 1,500 feet occur ... 1,718,791,281 tons 



Ditto between 1,500 and 3,000 feet do. ... 1,519,997,981 tons 



Ditto do. 3,000 and 6,000 feet do. ... 2,227,531,577 tons 



Ditto do. 6,000 and 9,000 feet do. ... 637,990,144 tons 



Total 6,104,310,982 tons 



Or, taking as before the total known available quantity to the 

 depth of 4000 feet to be 4219 millions of tons, and beHeving 

 that to be the limit of extraction under existing appliances, at 

 the rate of 1,000,000 of tons per annum, we may infer that 

 4000 years will elapse before coal to that depth will be exhausted. 

 The largest quantity of coal lies at the depth of from 3000 to 

 6000 feet ; but until the shallower measures are exhaiisted, this 

 will probably remain untouched. In futui'e years, however, as 

 our wants increase and our experience becomes greater, there 

 would appear, under the advanced appliances of scientific re- 

 search, no insuperable difficulty in reaching and working coals 

 at depths between 4000 and 6000 feet. 



Mr. Etheeidge further entered into and described the specu- 

 lations as to th^ probability of the Bristol coal-field being 

 repeated to the east of its present known limits, and also south 



