AMERICAN INDUSTRIES SINCE COLUMBUS. 149 



constructed as shown in Figs. 3 and 15, were invented in Ger- 

 many in the latter part of the sixteenth century ; the exact date, 

 as well as the inventor's name, is uncertain. Bellows working 

 on the principle of those used in accordions and concertinas have 

 also been known for many centuries. An engraving, showing 

 such bellows in use blowing a furnace, is given in the great work 

 of Agricola,* who also illustated rotary fan-blowers ; but these 

 evidently did not propel the air centrifugally, as does the modern 

 fan-blower, but pushed the air forward, very much as a revolv- 

 ing paddle-wheel pushes water. 



Another very curious apparatus for blowing furnaces and 

 smiths' fires is called a trompe. It consists of a vertical pipe, 

 usually made of wood, of a length suited to the fall of water. 

 Near the top of this pipe there are pierced a number of com- 

 paratively small lateral openings which incline downward in their 

 passage through the thickness of the sides of the pipe, whose 

 lower end enters the closed top of a barrel or other air-tight ves- 

 sel, from which proceeds a tube to convey the air to the furnace 

 or forge. This contrivance operates as follows : The descending 

 column of water in the pipe draws in air through the lateral 

 openings near its top, and this air is carried down by the water 

 and separates from it in the interior of the barrel and then passes 

 to the forge by the discharge-pipe, the water escaping through a 

 hole at or near the bottom of the barrel. Percy, f speaking of this 

 very simple blowing apparatus, says, " It is said that it was in- 

 vented in Italy in 1G40." But it must have originated at a much 

 earlier date, as Branca J gives three applications of it, illustrated 

 by engravings, and it is very probable that this highly ingenious 

 method of employing the fall of water to compress air was known 

 and used hundreds of years before the time of Branca. 



The early American forges and furnaces were blown either by 

 the ordinary leather bellows (Fig. 1), or by wooden cylinders 

 called "blowing-tubs," or by the trompe just described, and there 

 are still to be found in use a few examples of each of these primi- 

 tive methods of " raising the wind." In Fig. 2 we have an illus- 

 tration of a pair of " blowing-tubs " such as Overman # describes 

 as " the best form of wooden blast-machine." The figure shows 

 a vertical section through the axes of the upright 'blowing- 

 tubs," a a, and the " wind-chest," b, placed immediately above 

 them. Air enters the tubs from beneath and is purnped by the 

 pistons d d, with the aid of the "clack-valves" shown in the fig- 

 ure, into the wind-chest. The pressure of the air in the wind- 

 chest is determined by the weight h suspended at the lower end 



* De Re Metallica, Basilae, 1546. % Lc Machine, Roma, 1629. 



I Metallurgy, Iron and Steel, Loudon, 1864. ** The Manufacture of Iron, Philadelphia, 1S50. 



