139 



chimney or tower. The superintendent of an extensive mining 

 locality assured me that an ore, which by assay was proved to 

 contain 80 per cent, of metallic lead, would aflford 74 per cent, 

 in the reverberatory furnace, and only 64 per cent, in the 

 blast-hearth. 



" Notwithstanding this weight of evidence against the 

 blast-hearth, it is not without its advantages. In inland si- 

 tuations, where land-carriage and consequent high price of 

 fuel and other materials renders economy in these articles a 

 countervailing consideration against the smaller produce of 

 lead, the blast-hearth is a resource not to be contemned. 

 When the supply of ore is not abundant, a reverberatory fur- 

 nace would work to a great disadvantage : in such case the 

 blast-hearth is, of course, to be preferred. 



" There are some ores of so refractory a nature that the 

 reverberatory furnace is very tardy in delivering its run of 

 lead, although at length it gives such good produce : mean- 

 while expenses are accumulating. The ore raised from what 

 in Flintshire is called a blue stone, which includes schist, 

 mica-slate, and clay-slate, is much more refractory than 

 what is raised from a white stone, that is, limestone : when 

 raised from flint-stone the smelting becomes exceedingly 

 difficult, and the quality of the lead produced is generally 

 bad. In some such cases the blast-hearth has the advantage. 

 A remarkable instance of this kind occurred at the Wheal- 

 Betsy Mine, within five miles of Tavistock, in Devonshire. 

 The ore obtained in that mine was refractory, and could with 

 diflSculty be smelted : the reverberatory furnace, in fact, might 

 be said to have failed. The blast-hearth was then tried, and 

 a produce, which corresponded much better with the assay, 

 was obtained. The ore was, however, partially desulphurated 

 in a small reverberatory, before it was transferred to the 

 blast-hearth. Mr. Sadler says that two good smelters will 

 smelt at the blast-hearth six bings of good ore a day, which 

 are equal to about two tons eight cwt., short weight, that is, 

 5376 lbs. 



