Records of Mining. 299 



casioned considerable doubt as to the accuracy of the observations, 

 or of the methods by which it has been determined. 



Mr. Taylor, as may be expected, defends the statements which 

 come from a quarter in which he is so much engaged. He has taken 

 a historical survey of the evidence upon this subject, from a very 

 early period, and compared the account given by Smeaton of at- 

 mospheric engines as they were in 1765, with others in the time of 

 Boulton and Watt, and again with those most recently improved. 

 The result is curious, if it be correct ;— that as much power is now 

 obtained from one bushel of coal, as in the earliest periods was to 

 be had from seventeen bushels. 



The mode of estimating the duty of steam-engines is explained, 

 and a reference is made to the accounts which have been regularly 

 published in Cornwall since the year 1813, of which an abstract in 

 the form of a table is given, showing the average duty reported in 

 each year of all the engines working, and the average duty of the 

 best engines at each period. 



From this table we extract the following results : 



Average duty of Average duty of 



Years. Engines working. the whole. the best Engines. 



1813. 24- 19,456,000 26,400,000 



1828. 54 37,100,000 76,763,000 



If this can be shown to be correct, there can be no doubt but 

 that improvement in this as well as in other things has been progres- 

 sive. Mr. Taylor supports the authority of these reports, by some 

 statements exhibiting the diminished consumption of coal, in mines 

 in which the water',lifted is the same as formerly, and where the depth 

 has been increased. This is a fair way of coming to the proof, and 

 the facts must speak for themselves. 



The work also contains tables of the produce of the mines of cop- 

 per, tin, and lead, in Great Britain, with an account of the prices 

 of the former for several years, and an estimate of the home con- 

 sumption and export of those metals. 



We should be glad to see statistical accounts of this kind more 

 attended to by the miners in this country ;— in other states they are 

 regularly collected and published : we believe that it is difficult here 

 to obtain them accurately ; but we would recommend the Editor to 

 extend his inquiries upon this subject. The iron made in England 

 is supposed to be near 600,000 tons in a year; and several other me- 

 tallic products come from our mines. We believe that 100,000 ounces 

 of silver are extracted annually from our lead ; and we have also a 

 considerable quantity of manganese, besides zinc and antimony. 



If persons in various mining districts would contribute informa- 

 tion on this and various other interesting points, the " Records of 

 Mining" could not fail to advance the progress of useful knowledge. 

 The work is illustrated by many plates, some of which are beautiful 

 specimens of the state of the arts of drawing and engraving, as 

 applied to mechanical subjects. 



2Q2 XLVI. Pro- 



