52 EIGltTIl REPORT — 1838. 



The lead used in the original experiment was what is considered rich 

 in silver; it contained 10 oz. 15 dwts. 8 grs. per ton, and was divided 

 into a crystallized portion, found to contain 25 oz. 4 dwts. 21 grs., and a 

 fluid portion, holding 79 oz. 1 1 dwts. 12 grs. per ton ; the latter being ne- 

 cessarily much smaller than the former in quantity. The experiment 

 was repeated a great number of times upon lead of every variety as to 

 proportion of silver, with the same general result ; but being always pef- 

 formed in a crucible upon small quantities of lead, which of necessity 

 cooled quickly, the crystallized portion was never entirely deprived of 

 its silver, nor indeed reduced below two or three ounces per ton. 



It was not until the spring of the year 1833 that the author was con- 

 veniently circumstanced to proceed in applying to practice the principle 

 he had developed; but at that time his attention was again directed to 

 the subject, and he began by providing large pots of cast iron, in each 

 of which he could melt together and crystallize several tons of lead. All 

 the phenomena of crystallization in the large way were speedily observed, 

 Avhich, with the mode of conducting the operation adopted then and since 

 continued without alteration, may be thus briefly described. Four or 

 five tons of lead being melted in one of the pots, the metal was carefully 

 freed, by skimming, from all dirt or oxide, and its surface made quite 

 clean ; it was then suffered to cool very slowly, care being taken to 

 break off and mix with the fluid mass, from time to time, any portion 

 that might congeal on the sides of the pot : when the temperature had 

 fallen suflficiently, small solid particles or crystals began to form, princi- 

 pally upon the surface of the melted mass. These, if suffered to remain, 

 would have cohered together and formed a solid crust ; but being con- 

 tinually struck, and the whole body of metal kept in motion by constant 

 stirring, they sunk doM'ii to the bottom of the pan, and soon appeared 

 in considerable quantity. By means of a perforated iron ladle, the cry- 

 stals were taken out of the pan from time to time as they formed, and 

 placed in another pot, the liquid lead being drained out of them as much 

 as possible, and suffered to flow back into the original pot. In this way 

 the operation was conducted until two-thirds or three-fourths of the ori- 

 ginal lead was crystallized and withdrawn from the pot. The author 

 now found, as before, that the crystals always contained much less silver 

 than the lead from which they were formed ; but still he did not succeed 

 by one or even by two crystallizations, when operating with lead con- 

 taining eight ounces of silver per ton, in making them sufficiently poor: 

 for instance, a pot filled M'ith 8 ounce lead would yield at first crystals 

 holding from 1 to 2 ounces of silver ; in a little time, as the lead in 

 tlie pot became richer by receiving silver from the previously formed 

 crystals, it yielded crystals of 2 to 3 ounces ; and the crystals became 

 jH'ogressively richer, until, in the end, the original lead was divided into 

 three parts of crystalized lead holding about 4 ounces, and one part li- 

 quid lead holding about 20 ounces per ton. Upon the lead of 4 ounces, 

 as well as upon tTie lead of 20 ouuces, the operation miglit evidently be 

 repeated without limit, until the crystals became nearly free from silver 

 on the one hand, and tiie liquid lead exceedingly rich on the other ; but 

 this seemed to involve so much labour and delay, that the author wa^ 



