1889-90.] ARSENIC AND SULPHUR. 143 



mean to say that it is lowered considerably, as I have melted them at 

 about an incipient cherry red, corresponding to a temperature of about 

 8oo°C, and perhaps a few degrees lower, so that I can vouch for it as 

 being correct. If the melting point of silver be added, namely, I023°C, 

 the sum will = 2460, the mean, 6i5°C. I may say I have melted them 

 at such a temperature and below it. 



Many of our ores carry sufficient S and As for this law to be taken 

 advantage of in their treatment ; but before we can see in what way it 

 would be advantageous to us, we must consider another law. That law 

 is namely the spheroidal form given to small portions of metals or alloys 

 under three different modes. 



This IS a law which none of the works as yet published on Metallurgy 

 have mentioned, and I don't think that any of our profession have paid 

 any attention to it, and that some are even ignorant of its existence. We 

 shall consider the modes under which this form is given. 



1st. When metals in a thin body or sheet, such as gold leaf, are ex- 

 posed to certain temperatures the sheet breaks up and forms into globules. 

 This may be proven by taking any gilded work, say for instance on wood, 

 and placing it on the lid ot a furnace or common stove. When the wood 

 begins to char the gold will be seen to form into globules. This is caused 

 directly by the heat. 



2nd. When certain metals are alloyed with others, they cause a shrink- 

 age concentrated to a certain spot, which acts as a nucleus around which 

 another portion of the alloy forms a globule when cast upon a cold sur- 

 face, into water, or when pressed from under or through a crust of part 

 of the alloy solidified. This is caused, ist, by one of the constituents 

 cooling more quickly than the rest. 2nd. When one of the constituents 

 has a greater shrinkage power than the other. 



We can again take shot lead into account. As I have said it is an 

 alloy of arsenic and lead. Arsenic is of nature a great shrinker or con- 

 tracter, and thus it is used to give the rotund form to the lead, as it 

 causes it to contract when it touches any solid body and form a ball. 

 We ma}^ further prove this law by taking an alloy that is known to 

 shrink, melt and cast into an open mould, let the top solidify, strike it 

 two or three gentle taps with a hammer or die, having a broad striking 

 surface, when the metal will be seen to force its way up through the crust 

 and form globules on the surface. 



The 3rd mode really belongs to the former two, but we will consider 

 it as an independent one. It is the action of the atmospheric pressure 

 in the promotion of a spherical form in molten metal, when in small 



