1886.] on the Electrical Deposition of Dust and Smoke. 527 



Application of the Coagulating Power of Electricity to practical 



purposes. 



In many industries the presence of fine dust or fume suspended 

 in the atmosphere is highly objectionable, sometimes because of the 

 poisonous or dangerous nature of the dust, sometimes because it is 

 valuable and apt to escape and be wasted. 



In flour-mills and coal-mines, the fine dust is dangerously explo- 

 sive. In lead, copper, and arsenic works it is both poisonous and 

 valuable. 



Mr. Alfred Walker, of Walker, Parker & Co., first informed me 

 of the difficulty which lead-smelters labour under in condensing 

 the fume which escapes along with the smoke from red-lead smelting 

 furnaces, and he wished to put an electrical process of condensation 

 to the test on a large scale. 



The devices which are in use at difterent works to collect or 

 condense this fume are very numerous, and some of them very 

 cumbersome. Prof. Eoberts- Austen has been kind enough to lend me 

 diagrams illustrating several of these contrivances. 



At Bagillt the method used is a large flue two miles long, coiled 

 up in the side of a hill between the furnace and the chimney ; 

 much is retained in this flue, but still a visible cloud of white lead 

 fume continually escapes from the top of the chimney. 



The only difficulty in the way of depositing fume in the flue 

 by means of a sufficient discharge of electricity, is the violent 

 draught which is liable to exist there, and which would blow away 

 mechanically any deposited dust. In some ways the blast may be 

 helpful, for instance, by keeping the electrical points clear and pre- 

 venting local clogging, but a large chamber must be provided 

 somewhere for the coagulated flakes of dust to settle and remain in 

 calm. 



The plan I suggest at present is to line a certain portion of the 

 interior of a flue with spikes, and then to hang in the middle of it 

 wire netting, well insulated and studded all over with ragged edges 

 and points. It may be suspended lengthways in the flue. If the 

 chamber be very large, it may be well to have a number of long prickly 

 nets arranged parallel to each other, and kept alternately positive and 

 negative. 



The insulation of the suspended conductor, whatever its shape, has 

 of course most carefully to be arranged : everything depends upon that. 



[Experiment showing the action of an electrical point held above 

 a model chimney emitting smoke. Its first efioct is to destroy or 

 reverse the draught : but if the chimney be itself provided with 

 points at the top, and an electrified cap be held over it, e. g. a small 

 Bheet of prickly wire gauze, the draught is assisted, and the smoke is 

 mainly condensed.] 



I do not regard this as a good method of dealing with smoky 

 chimneys : the right way to deal with them is to abolish them, i. e. to 

 make combustion so perfect that no unburnt matter escapes. 



Vol. XI. (No. 80.) 2 m 



