Mr. Farerfs Account of the Rivdrs, cic. in Derby shire. 191 



added to a mixture of lead and sulphur, it will absorb the 

 sulphur, leaving the lead in its metallic form: might it not 

 be useful to flux sulphureous lead ores in conjunction with 

 the scales or other refuse pieces of iron, or even with some 

 sorts of iron ore? The smelter's great care should be to 

 extract as much lead as possible at the first operation of 

 smelting the ore, and to leave the slag as poor as possible ; 

 but if he should still find either the slag of the cupola fur- 

 nace, or that of the hearth furnace, containing much lead, 

 (as that even of the hearth furnace certainly does.) he may, 

 perhaps, find it worth his while to reduce the slag into a 

 powder by a stamping mill, or by laying it in highways to be 

 ground bv tlie carts, aiid then he may separate the stony part 

 of the slag from the metallic, by washing the whole in water, 

 inasmuch as the metallic part is far heavier than the other. 

 " I estimated the weights of several pieces of slasx, and 

 found them to differ very much from each other ; this dif- 

 ference is principally to be attributed to the different quan- 

 tities of lead left in them. 



Weight of a cubic fool of 



Avoir.oz. 



Slag from a cupola furnace, where no lime was used 3742 



Black slag from a hearth furnace 3632 



Another piece 36 12 



Black slag from another hearth furnace; struck fire 



with steel 3378 



Black glass slag 33 71" 



XXVIII. Extracit from Mr. John F.kwky's first Folmne 

 of Report to •' he Board of Agriculture, on Derby skirc * ; 

 giving an Account of the several Rivers in thai Cuunlij^ 

 and of the particular Strata intersected and' exposed by 

 the excavated Vallkys through which they flow ; of their 

 Floods and of the Water faUs In their course, arid else- 

 where ; with an Account of the Acres of surface f-ovi. 

 tvhich each Rivt^r collect'i its IFaters : on the absence of 

 Lakks in that County, is'c. 



[The Readers of the Philosophical Magazine will recollect, 

 that during the preparing and printing of the Volume 



* This Volume of important matter relating to the Surface, Stratification, 

 and Minerals of Ut-rbyshire and the bbrders of its seven adjacent Counties, 

 jiurports to be intended as, and I sincerely hope ifi time will prove to be, 

 ///'■ firft of a Siriis of copious Reports, undirrraken with the view of investi- 

 j^atinj; »nd e)i]>laiiiing the physical Gci)gT;ii)hy, Str.itiiication, and Minerals, 

 til the British Llands; with inforniatio:i, v.hicli cannot fail of I)ein^impor- 

 tnut in a national point (jf view, of tlie uses to which the mineral products 

 ill our koil, arc or ;r.ay be applied. — JiDiTOK, 



above 



