Diffusion of arsenical Vapoursfroni Copper-smelting Furnaces. 35 



with soot and a white crust, probably arsenic, and sulpliur 

 over the bottom and lower part of the sides. Nos. 3, 4, and 5, 

 presented soot, with a superstratum of sulphur, in considerable 

 quantities. Mr. Young thinks that the three flues contained 

 from i cwt. to 1 cwt. of deposit, the 6th and 7th soot, and a 

 smaller quantity of sulphur; the 8th coal-tar, which continued 

 to form onto the 14th, gradually diminishing, accompanied by 

 very little sulphur. From the 16th to the end, thei-e was no 

 dejjosit worth notice, and the bricks and mortar of the 24th 

 were not even discoloured. On lighting the furnace to-dny 

 the smoke was ten minutes in reaching the mouth of the staclv,^ 

 After the fire was well up, we threw in a bundle of wet straw, 

 and observed that tlie smoke arising from its combustion ap- 

 peared at the mouth of the stack in tliree mmutes." Tlie re- 

 porter proceeds to observe, " It now appears, in the undeniable 

 shajje of experimental fact, that the noxious parts of cojiper- 

 smoke may be effectually controlled and compelled to stay 

 in-doors without any chemistry besides that which natpre hnv 

 nishes. Bricks and mortar, and a tolerable mason, are all the 

 array of power and science which need be called into action. 



The draft in your flues is so perfect, that Mr. , a manager 



of copper-works, who furnished the ore, cautioned the man 

 against allowing the fire to become too intense for the process 

 of' calcination ,- and there is no doubt that several luuulred feet 



of flue might be added without impeding the draft. Mr. , 



however, tliinks that all which now escapes may be consumed 

 by combustion: we have no doubt on the subject." 



The writer of the foregoing letters, having been warned 

 against trusting too implicitly to first impressions, on a single 

 attempt to reduce principle into practice, writes on the 28th 

 Marcli as follows: — " In the detail which I sent you, I beheve 

 I did not observe, as I should have done, that the ore was as 

 well calcined in as short a time, and without more fuel, as is 

 used in the ordinary flues; — this by way of supplying an ap- 

 prehended omission. Now for the objections which have jire- 

 scDted themselves, either in the siuijie of my own ideas or the 

 sai/in^s of others. It did occur to me that the nexvncss t)f thq 

 flues might oj^erate favourably in expediting the process of con- 

 densation and precipitation. It was also said, that the fresh 

 mortar would have a chemical action on the acid particles ot 

 the smoke, anil thus neutralize one j)art of the niischiel. A 

 jiuestion has also been started, whether there- can be sufficient 

 (traught obtained through such a length of (hie to melt the ore 

 alter calcination. On this last point I have felt doubts, but 

 the siiperintendant says he fi-els no doubt on the subject; and 

 states, that, ilanv such dinicultv should arise, he would shorten 



!•: 2 the 



