BLAST APPARATUS. 663 



ami F, acting as valves; each is provided with a crescent-shaped abutment aud recess, 

 which allow the wings of the fan C C' to pass it. The three drums are connected by 

 suitable gearing ou the outside of the case, as is shown in Fig. 1, in such a manner 

 that the revolutions of the drum-valves draw air isochronously with those of the 

 fan-drum. By their combined operation air is drawn in at one side of the apparatus at 

 the ordinary pressure and compressed at the other to the pressure required, this press- 

 ure being in direct proportion to the velocity of the drum, as indicated in Table VI. 



The blower is placed on a brick chamber, M (Fig. 2), connected with a sheet-iron 

 pipe, JV, through which air is drawn. This is the best arrangement, for by its mean? 

 accidents which might result from the introduction of dust are prevented, aud mean- 

 while concussion of air is avoided, which renders the machine comparatively noiseless. 

 But the sheet-iron pipe N is often dispensed with, and air is simply drawn through 

 the grating R R', placed in front of the blower (Fig. 1). The blower is connected at, 

 with the general system of blast pipes by means of galvanized sheet-iron pipes, 

 which must be air-tight. When the apparatus is in full blast, a slight aud regular 

 pulsation is felt at two or three small holes placed at the rear of the case. Such is, in 

 all its simplicity, the Baker's rotary blower, the most perfect apparatus of the kind 

 ever used in smelting. 



The Root positive-blast blower The Root blower, manufactured by Messrs. P. H. & 

 F. M. Root, of Conuersville, Ind., is shown in perspective (Fig. 3, Plate XLII) and in 

 vertical section (F'ig. 4). These sketches are copied from the maker's engraving of a 

 No. 5 blower, delivering 23J cubic feet of blast per minute revolution. It is the Roots' 

 new style of blower, formed entirely of metallic parts and less delicate in the details 

 of its construction than the old style. This machine, like the Baker blower, is very 

 simple and effective, aud gives a positive blast in nearly every part of the case, pro- 

 portionate to the number of revolutions. The external parts of the Root blower con- 

 sist of two semicircular cast-iron cases, A and B, screwed and bolted to two cast-iron 

 end plates, 8 8', which serve also as supports to the whole machine and to the cast- 

 iron blast-pipe and air chamber M ; of five cast-iron journals, J~j five phosphor- 

 bronze journal-boxes, K ; two cut-gears, protected by the housing, H, aud one driving 

 pulley, P. 



The internal-blast contrivance consists of two cast-iron revolvers, C C", mounted 

 on steel shafts, II'. Each revolver acts as a fan-drum and drum-valve, with recess 

 aud abutments, forming the very simple and ingenious contrivance seen in Fig. 4. As 

 with the Baker blower, the blast-pipe is connected by means of an air-tight gal- 

 vanized sheet-iron pipe with the general system of blast-pipes distributing the blast 

 to the tuyeres of the furnaces. 



Blast-pipes A glance at Table IV will show that at each smelter the number of 

 blowers in use corresponds to the number of furnaces at work, and as a matter of 

 course the capacity numbers of the blowers correspond to the smelting capacity of 

 the furnaces. The furnaces of Leadville being always worked with several tuyeres, 

 the blast is always distributed by branch pipes from an induction-pipe surrounding 

 the furnace. A glance at any of the descriptive sketches of furnaces accompanying 

 this report will show this arrangement, I always representing the induction pipes 

 and t/the branch pipes of the same. When the smelting works have only one furnace 

 the induction -pipe is placed in direct communication with each blower by means of a 



