Steam-Engines in Cornwall. 429 



18 14, when it was given up. It was undertaken again by the 

 present adventurers in 1826 ; it is not situated near other mines, 

 by which it can be suspected that water is drained from it, or 

 that there is now less to draw than formerly. It is worked 

 deeper than before, and the engines are more loaded in that 

 proportion. As greater steam power must therefore be re- 

 quired than in 1813 ; is that obtained by the use of a smaller 

 quantity of fuel ? and if so, is the diminution in quantity pro- 

 portionate to the improvement in engines, which we say has 

 taken place ; and has that improvement been correct!}' repre- 

 sented in the duty papers ? If it should appear to be so, then 

 the measurement of coal, the diameter of the pumps, and all 

 other data, have been correctly assumed and used, and for a 

 long series of years. 



I have given in the " Records of Mining" several instances to 

 show that the actual quantities of coal used by different mines 

 have diminished proportionately with the reported improve- 

 ment in the engines ; and I presume it will not be supposed 

 that the account books are incorrect, which show the quantity 

 of coals bought and paid for. I will repeat the case of Wheal 

 Towan, as it appears to me decisive, and as it is one with which 

 I am, personally, totally unconnected, and can have therefore 

 no partialities to bias me. 



When the mine ceased to work in 18 14, the average monthly 

 consumption of coal had been for some time 9360 bushels ; the 

 average duty of engines in Cornwall was then about 20,000,000, 

 according to the tables which I have given, and which we may 

 assume as the performance of those engines for this calcula- 

 tion. 



When I wrote my paper in the latter part of 1828, the 

 monthly consumption of coal at Wheal Towan was but about 

 2600 bushels, and the average duty of the two engines working 

 was 66,000,000, as reported in the duty papers. 



Now 66,000,000 is to 20,000,000 as 9360 is to 2830, which 

 is sufficiently near to prove the case; and in taking a larger 

 average of the coal, and since my paper was published, 1 find 

 the monthly quantity is increased to 2900 bushels, the time 

 including winter months, when there is more water to draw, 

 and the depth of the mine is somewhat increased. The average 

 duty of the engines has in the same time advanced to near 

 70,000,000; and calculating as before, 70,000,000 is to 20,000 

 as 9360 is to 2674, which shows a very near approximation 

 to what would be inferred from the actual quantity of coal 

 supplied. 



There is therefore every kind of proof that the application 

 of steam has been improved so as to occonomize fuel in Corn- 

 wall, 



