BLOWING ENGINE. 



617 



Slewing BLOWING Engine, is a machine for forcing air 

 Engine. w ith great velocity into a furnace in order to increase 

 """^V"-"" - the combustion and is now used in all the practical 

 operations of metallurgy. 



The machine first employed for this purpose was a 

 pair of leather bellows wrought by the hand ; but when 

 it became necessary to smelt iron in large quantities, the 

 size and number of the bellows were increased. 1 wo 

 pairs of bellows were so connected by means of a le- 

 ver, that the one pair shut when the other opened. 

 The handle of each pair was* successively moved by 

 two cogs, placed at right angles to each other on the 

 horizontal axis of a water wheel ; so that during the 

 revolution of the wheel, one of the cogs shut one pair 

 of bellows, and forced the included air into the fur- 

 nace, while the other, which was at this instant open- 

 ed, was shut by means of the other cog, and thus 

 discharged its contents into the furnace. By this 

 means a continued blast is kept up, excepting a 

 trifling pause when the motion is changed. A ma- 

 chine similar to this, called the slag-mill, is used for 

 refining the lava from the reverberating furnace in 

 which lead ore is smelted. 



Another engine, called the water blowing machine, 

 has been used for producing a 6trong blast. It has 

 been pretty generally adopted on the continent for 

 more than a century, but does not seem to have 

 come into use in this country. A current of water 

 is made to pass through a kind of cullendar placed in 

 the open air, and perforated with a number of trian- 

 gular holes. The water descends through these 

 apertures in$ggfff small streams, and by exposing a 

 great surface Ho the atmosphere, it drags along with 

 it an immense quantity of air, and is conveyed 

 through a tube till it dashes against a stone pedestal 

 inclosed in a large vessel. The mixture of air and 

 water which falls upon the pedestal is dispersed in 

 every direction ; the air is separated from the water ; 

 it ascends to the upper part of the vessel, and rushes 

 through a pipe to the furnace, while the water de- 

 scends through apertures at the bottom of the vessel. 

 Fabri and Dietrich im?gir.cd, that the wind is oc- 

 casioned by the decomposition of the water, or its 

 transformation into gas in consequence of the agita- 

 tion and percussion of its piirts ; bnt M. Venturi, 

 [Experimental Inquiry cona nrug the lateral com- 

 municalion of motion in Fluid*, Pro VIII.) to 

 whom we are indebted for the first philosophical ac- 

 count of this machine, has shewn, that his opinion is 

 erroneous, and that the wind is lupplied from the at- 

 mosphere ; for when the lateral openings were shut, 

 no wind was generated. . 



Hence the principal object in the construction of 

 these machines is to combine as much air as possible 

 with the descending current. With this view, the 

 water is often made to pass through a cullendar, as al- 

 ready mentioned. 



Franciscus Tertius de Lanis, ( Magixtero Nat. et Ar- 



tis, lib. v. cap. 3. ) observes, that he has seen a greater 



wind generated by a machine of this kind, than could 



be produced by bellows ten or twelve feet long.* 



Machines of such a nature might have been suffi- 



Ferguson's Lecture*, by Dr Brewster, Vol. II. p. *15. 

 Nicholson's Journal, Vol. XII. p. 4. 

 VOL III. PARI IV. 



cient for smelting iron when charcoal was used for Blowing 

 fuel as in other countries ; but when coal began to 

 be used, it became necessary to construct machines 

 capable of affording a powerful and constant blast, 

 and formed of the most durable materials. 



The earliest contrivance of this kind was a forcing 

 pump, worked by a water wheel, or a steam engine ; 

 and it would appear, that the first cylinders of this 

 kind, at least those of any magnitude, were erected 

 by Mr John Smeaton, in 1760, at the Carron iron 

 works. The pumps were wrought alternately by a 

 water wheel, having four cranks upon its axis, each of 

 which moved the piston of a cylinder, which had a 

 stroke of four feet six inches ; the diameter of each 

 cylinder being also four feet six inches. 



In situations where a fall of water could not be 

 obtained, steam engines were employed to work the 

 pumps ; but as these machines were then only single, 

 the piston descending by the pressure of the atmo- 

 sphere, it was necessary to have some contrivance for 

 producing a continued stream of air during the de- 

 scent of the piston. This object was effected, by re- 

 ceiving the air into a regulating cylinder of the same 

 size as the blowing cylinder, and furnished with a 

 piston loaded with heavy weights. As every stroke 

 of the engine would pump into this cylinder twice 

 the quantity of air that would pass through the nose 

 pipe into the furnace in the same time, the air raised 

 the loaded piston of the regulating cylinder, and du- 

 ring the time that the engine ceased to act, the weight 

 of the regulating piston forced the air into the fur- 

 nace. This method of regulating the blast, which 

 continued in general use for many years, has been 

 superseded by the water regulator, and by the dou- 

 ble acting blowing cylinder, wrought by a steam en- 

 gine of Watt and Boulton's construction. 



An engine of this kind, of large dimensions, is re- 

 presented in Fig. 1. of Plate LXIII. It is wrought Platb 

 by a steam engine of thirty-five horse power, with a LXIII. 

 steam cylinder of thirty-three inches diameter, acting F 'S - ' 

 with a seven feet stroke. On the opposite end of the 

 beam from the steam cylinder is jointed the rod D, 

 which fs turned exceedingly true, so as to move 

 through the stuffing box without allowing any air to 

 escape, and without any unnecessary friction. A 

 quantity of hemp is placed round the rod in the box 

 a a, which forms part of the lid of the cylinder, and 

 is held tight by the iron nuts bb. The piston is fit- 

 ted to the lower end of the rod D, and is packed 

 with leather so as to fill exactly the internal diameter 

 of the cylinder A A.. To this cylinder are fixed four 

 necks, B, F, G, H ; two of which, B, F, contain 

 the suction valves, by which the air enters the cylin- 

 der, while the other two contains the forcing valves, 

 through which the air is expelled at every elevation 

 and depression of the piston into the chambers 1, K, 

 and through the pipes L, M, into the regulating re- 

 ceiver OP, which is of the form of a parallelopipedon, 

 or an inverted box without the lid, and is immersed 

 in a cistern R.S, filled with water. 



Let us now suppose that the piston is at the bot- 

 tom of the cylinder A A, and begins to be raised by 



See also Lewis's Commerce of Arts, the Journal its Mines, and 



4i 



