352 



EECEEATIVE SCIENCE. 



of this saving, the following figures may be 

 given. Let us set out with, lead, containing 

 10 ounces of silver to the ton. Now, formerly, 

 30 tons of such lead would have to be cupelled 

 in order to obtain 300 ounces of silver, while 

 by Pattison's process the whole 300 ounces 

 is concentrated in one ton of lead, which 

 alone undergoes cupellation, and the remain- 

 ing 29 tons have only to be remelted, and 

 sent into commerce as pure lead. 



To see this wonderful application of scien- 

 tific knowledge in full operation, we enter a 

 lofty building, open at either end, in which are 

 ranged a series of eight cast-iron cauldrons, 

 set in brick fire-places. Each of these is ca- 

 pable of containing ten tons of metal, which 

 is the pig-lead from the smelting furnace. 

 When the whole mass is melted, the fire is 

 reduced to a degree, which vrill just keep the 

 lead a little below the melting point. A very 

 gradual process of cooling is, therefore, taking 

 place. It so happens that there is but one 

 of the pots being worked when we enter, so 

 that we run no risk of failing to understand 

 what is going on. First of all, then, there is 

 the man who keeps incessantly stirring the 

 molten mass, until he feels, by the resist- 

 ance to the iron paddle with which he works, 

 that a quantity of lead crystals have collected 

 at the bottom of the pot. Then he takes an 

 immense perforated ladle, and crushing the 

 blue film upon the surface of the leaden sea, 

 it sinks slowly into its depths. A chain is 

 now attached to the handle, and the other 

 end being made fast to the windlass — the 

 fulcrum of this long lever being the edge of 

 the melting pot — a few quick turns bring the 

 ladle up, almost bending under the weight of 

 its burden, while through the perforations 

 the enriched lead falls in, literally, a silvery 

 shower. But as the lead crystals still retain 

 melted metal in their interstices, the work- 

 man again and again shakes the ladle, until 

 not a drop more will come from it. The 

 crystals, which are granular and agglome- 

 rated by fusion, so as to resemble a dull gray 



sandstone, are passed into another pot, where 

 they are, with a new supply, subjected to a 

 repetition of the operation, while the enriched 

 lead is further treated in the same manner, 

 until it contains about 300 ounces of silver in 

 a ton. Further than this it is not found pro- 

 fitable to go. This, then, is Pattison's desil- 

 vering process, founded upon what but for 

 his genius might have been, if known at all, 

 merely a scientific abstraction. 



The Pattisonized lead, now rich in silver, 

 is handed over to the refiner. Unfortunately, 

 we cannot follow it through the very inte- 

 resting process of cupellation, for this is only 

 performed at Ballycorus when a sufficient 

 quantity of the alloy has been accumulated 

 to yield a cake of silver of some 6000 ounces. 

 We can, however, inspect the furnace, and 

 get some idea of how it is performed upon 

 so large a scale. 



The hearth of the furnace is so con- 

 structed as to admit of the cupel, or " test,' ' 

 being placed upon it. This is a fiat dish, 

 about two feet long by eighteen inches wide, 

 and is made by pressing into an iron grating, 

 which forms at the same time a model and 

 a support, a quantity of a paste made of 

 finely ground bone-ashes mixed with water. 

 Now, not far from the cupel, and com- 

 municating with it by means of a narrow 

 channel cut in the setting of the furnace, 

 is a small melting pot. Matters are so 

 ordered, that the pot being full of melted 

 metal, some of it shall run into the cupel. 

 The fire is now urged to its greatest 

 intensity, and a strong blast of air being 

 established, by means of a fan, the lead 

 becomes rapidly oxidized, and the metal 

 oxide floating upon its surface is swept off 

 by the current of air, much as you would 

 blow the froth from a glass of champagne, 

 and falls into a pot placed to receive it. And 

 could we see all this, a still more interesting 

 sight would await us at the close of the ope- 

 ration, when the last vestiges of the lead were 

 passing away. Up to this time the surface of 



