VOL. XVII.] PHILOSOPHICAL TRANSACTIONS. 517 



that they may lose none of their ore, into sieves made of strong wire at the 

 bottom ; and these sieves, with the calamine, lead, and the remainder of the 

 earthy, sparry, and stony parts, which the water could not wash away, they 

 often dip and shake up and down in a large tub of water, by which means the 

 parts of the lead mixed among the calamine sink, or pitch down to the bottom 

 of the sieves, being the heaviest, the parts of the calamine in the middle, and 

 the other sparry, stony, and trashy parts rise up to the top ; which as they rise 

 they skim off and throw among the rest of the rubbish : then they take off the 

 calamine, and lastly the lead. When they have thus cleansed the calamine, as 

 well as they can, to cleanse it still more, they spread it on a board, and so pick 

 out with their hands the trash and stones that remain. But all of it does not 

 require so much trouble; for some rises out of the works large enough to be 

 cleansed and picked fit for the calcining oven, without all this charge and 

 pains; and there are several loads of this large calamine, which have no mixture 

 of earth or trash. 



After they have prepared the calamine by washing and picking it, they then 

 carry it to the oven, which is much larger than a baker's oven, but made much 

 in the same fashion ; only the way of heating, burning, or baking the calamine, 

 is different ; for it is not done as bread is, for they cast in their coals into a 

 hearth made on one side of the oven, which is divided from it by a hem or 

 partition, made open at the top, whereby the flame of the fire passes over, 

 and so heats and bakes the calamine. They let it lay in the oven for 4 or 5 

 hours, the fire burning all the while, according to the strength of the calamine, 

 some being much stronger than others, and so requiring a longer time ; and 

 while it continues in the oven, they turn it several times with long iron coal- 

 rakes ; when it is sufficiently burnt, baked, and dried, they beat it to a powder 

 with long iron hammers, like mallets, on a thick plank, picking out what stones 

 they find among it ; so that at last the calamine is reduced to dust, and then it 

 is fit for sale. The dust of calamine it seems conduces much to the curing of 

 sore eyes ; and that it is frequently used for taking films off the eyes of horses 

 and other beasts. 



^n Arithmetical Paradox, concerning the Chances of Lotteries, By the Hon. 

 Francis Roberts, Esq. F. R. S. N° igs, p. 6/7. 



As some truths, like the axioms of geometry and metaphysics, are self-evident 

 at the first view, so there are others, no less certain in their foundation, that 

 have a very different aspect, and, without a strict and careful examination, rather 

 seem repugnant. We may find instances of this kind in most sciences. As, in 

 geometry, that a body of an infinite length may yet have but a finite magnitude; 



