(538) .. [Oaober, 



PROGRESS IN SCIENCE. 



MINING. 



The Royal Commission appointed some five years ago to inquire into the 

 probable duration of our supply of coal has recently issued its long-expected 

 Report. An enormous mass of information has been collected by the several 

 committees into which the Commission was resolved, and after much pains- 

 taking investigation, some important general conclusions have been attained. 



In attempting to fix a limit to the depth at which coal may be profitably 

 worked, it has been found that the chief difficulty arises from the increased 

 temperature consequent upon increased depth. With a view to determine the 

 maximum temperature compatible with the healthful prosecution of mining, 

 work, some experiments were made by Dr. J. Burdon Sanderson in a Cornish 

 mine, where the air was heated by a hot spring of 114I F. It appears that 

 the temperature at which work can conveniently be prosecuted depends greatly 

 on the hygrometric state of the surrounding air. At the working face of the 

 coal, air is always more or less humid, but the deepest collieries appear to be 

 the driest. On the whole, the Commissioners conclude that a depth of 4000 

 feet may be fairly attained. 



Another branch of inquiry related to waste in working coal. It appears 

 that under a favourable system of working the loss is only about 10 per cent, 

 but that in a large number of cases it amounts to as much as 40 per cent. 



The estimation of the quantity of available coal in the known coal-fields of 

 the British Isles was one of the main objects of the investigation. Taking 

 4000 feet as the maximum depth to which workings may be extended, and 

 excluding all seams less than one foot in thickness, it is estimated that there 

 exists in the several coal-fields of these islands, upwards of 90,207 millions of 

 statute tons of coal. In addition, however, to this amount, it is well known 

 to geologists that in certain districts vast tracts of coal lie hidden beneath the 

 Permian, New Red, and more recent strata. Taking into account only such 

 coal as will be found within 4000 feet of the surface, and deducting 40 per 

 cent for loss and other contingencies, the Commission estimates that not less 

 than 56,273 millions of tons of coal exist below these post-carboniferous 

 rocks. Adding this quantity to that known to exist in our coal-fields, we 

 obtain a grand aggregate of 146,480 millions of tons as the amount of available 

 coal in the British Isles. It remains to consider how long this supply is likely 

 to last. Assuming that our present rate of consumption — 115 millions of tons 

 per annum — remains constant, this amount of coal will not be exhausted for 

 1273 years. But such an assumption is obviously erroneous. Let the rate of 

 production increase at the rate predicted by Professor Jevons, and this 

 quantity will be exhausted no years hence. It is shown, however, by Mr. 

 Price Williams, that although the population of the United Kingdom rapidly 

 increases, yet the rate of increase is diminishing. Introducing this correction 

 into Jevon's estimate, it is shown that the supply will hold out for 360 years. 

 If instead of taking a geometrical increase in the rate of consumption, 

 an arithmetical increase be calculated by adding 3 millions of tons each year, 

 it is found that the supply will be exhausted in 276 years. 



Another interesting question discussed in this report is the probable exten- 

 sion of the coal measures beneath the newer rocks of the South of England. 

 Mr. Prestwich, following Mr. Godwin-Austen, argues in favour of this exten- 

 sion, but his views are strongly opposed by Sir Roderick Murchison. 



The prosperity of some of our colonies is so closely connected with 

 the development of their mineral wealth that colonial statistics of mining are 

 always of interest. From Mr. Brough Smyth's " Mineral Statistics of 

 Victoria for 1870" we learn that the quantity of gold exported from the colony 

 in that year amounted to 1,222,798 ozs., being a decrease of 118,040 ozs. on 

 the amount exported during the previous year. This diminution is certainly in 



