200 THOMSON ON CARNOT'S 



consumption of only 6J Ibs. of dross, equivalent 

 to 5 Ibs. of the best Scotch or 4 Ibs. of the best 

 Welsh coal, per horse-power per hour. The 

 economy may be estimated from these data, as in 

 the other cases, on the assumption which, with 

 reference to these, is the most probable we can 

 make, that the evaporation produced by a pound 

 of best coal is 7 Ibs. of steam. 



58. The following tables afford a synoptic view 

 of the performances and theoretical duties in the 

 various cases discussed above. 



In Table A the numbers in the second column 

 are found by dividing the numbers in the first by 

 8J in cases (1), (2), and (5), and by 7 in cases (4), 

 (6), and (7), the estimated numbers of pounds of 

 steam actually produced in the different boilers by 

 the burning of 1 Ib. of coal. 



The numbers in the third column are found 

 from those in the second, by dividing by 618 in 

 Table A, and 614 in Table B, which are respec- 

 tively the quantities of heat required to convert a 

 pound of water taken from the hot-well at 30, 

 into saturated steam, in the boiler, at 140 or at 

 121. 



cylinders, which have been recently added to them by 

 Mr. M 'Naught of Glasgow. 



