in a general sense, denotes an agitation of the air, whether performed with a pair of bellows, the mouth, a tube, or the like.

among gardeners, denotes the action of flowers in opening and displaying their leaves. In this sense, blowing is the same with flowering or blossoming.

The regular blowing season is the spring, although some plants have other extraordinary times and manners of blowing, as the Glastonbury thorn. Different flowers, also, as the tulip, close every evening, and blow again in the morning. Annual plants blow sooner or later according as their seeds are put in the ground; and hence the curious in gardening sow some every month in summer, to have a constant succession of flowers. The blowing of roses may be retarded by shearing off the buds as they are put forth.

**Blowing of Glass**, one of the methods of forming the various kinds of work in the glass manufacture. It is performed by dipping the point of an iron blow-pipe in the melted glass, and blowing through it with the mouth, according to the dimensions of the glass to be blown. See Glass.

**Blowing of Tin** denotes the melting its ore, after being first burnt to destroy the mundic.

**Blowing Machines**, in the arts and manufactures, and in domestic economy, are instruments for producing a continued current of air, principally for the purpose of facilitating the combustion of fuel. The first idea of such a machine was doubtless derived from the lungs, which we are constantly in the habit of using for the purpose of blowing, but more especially in the simple and useful application of the blow-pipe.

Of these different machines, the common bellows bears the greatest resemblance to the lungs, and was in all probability the first contrivance for artificial blowing. In the first instance, this instrument might be a simple bag, capable of distension by a mechanical force, the air being drawn in and pressed out of the same aperture in the manner of breathing. The first improvement upon this simple form would be to admit the air by a valve opening inwards when the bellows were distended, the blast outwards being from another aperture. This improvement consists in the air being admitted at a wider aperture, which fills the bellows in less time than would be required by the small pipe through which the air is allowed to escape. The blast, in this state of the machine, is not continuous, but in puffs, at intervals of time required for the air to enter the bellows through the valve; the blowing interval being to the filling interval as the areas of the apertures. This irregular blast was for some time remedied by employing two bellows which blew alternately, the blowing on one taking place while the other was filling. The inconvenience, however, was but partially remedied by this contrivance. The invention of what are called double bellows must have been considered a valuable acquisition in the art of blowing. But previous to describing these, it will be necessary to give a description of single bellows above mentioned.

It will be needless, however, to say more than refer the reader to common domestic bellows, which are in every respect the same as the single bellows first used. The leather nailed to the upper and lower boards is prevented from collapsing, when the boards are separated, by a hoop of wood contained within, performing the office of the ribs in the sternum of animals, without which the breathing would not be performed. The lower board contains the valve which admits the air. When the two boards are separated, the air lifts the valve in entering the cavity. When full of air, the closing of the boards causes the air within to close the valve, thus preventing its return in that direction, and compels it to escape at the pipe, the mouth of which is called the nozzle or nose-pipe.

In order to conceive the construction of the double bellows, we have only to take a third board of exactly the same shape as the other two, and connect it with the lower board by a piece of leather similar to that of the single bellows, making two cavities exactly similar, and separated by the lower board of the single bellows, which now becomes the middle board of the double bellows. The third board we shall now call the lower board. This latter has a valve in it exactly similar to the first, which still retains its place in the new construction.

The middle board is now fixed in a horizontal position, the pipe being placed to the fire to be blown. The lower board is held down by a weight, which keeps the lower cavity constantly full of air. The top board has a weight laid upon it, which presses all the air out of the upper cavity through the pipe.

The machinal action by which the blowing is performed is, first, to lift up the lower board. This forces the air from the lower into the upper cavity, the valve in the middle board preventing its return. The weight on the upper board now presses the air with a uniform blast through the pipe. During this time the lower board descends, which fills the lower cavity with air from the atmosphere; and this again rises and gives its contents to the upper cavity, and thence passes through the nose-pipe. Hence we see that that irregular puffing blast which belongs to the single bellows is here confined to the lower board, which supplies air to the upper cavity, while the upper board is constantly pressing uniformly upon the air in it. Although this is a considerable improvement upon the single bellows, it does not completely obviate the irregularity of the blast. So long as the lower board is not in action, the pressure on the upper board being uniform, the blast is the same. Every time, however, the bottom board rises to force the air into the upper cavity, an extra pressure is given to the air in the upper cavity, and a temporary puff is produced. In the application of bellows to the smith's forge, the continued blast was of less importance than in the blast-furnaces applied to the smelting or refining of ores. The single bellows are at present almost exclusively employed by anchor-smiths and cutlers; while the blacksmith and most others use double bellows, which are doubtless better for all purposes.

In France and other parts of the Continent, bellows wooden have been formed entirely of wood, instead of the flexible bellows sides of leather, which serves to increase and diminish the capacity. The wooden bellows consist of two boxes, each open on one side, the one being just capable of containing the other; the outer box being placed with the mouth upwards, the other is made to descend into it with the mouth downwards, the latter being capable of moving up and down, while the other remains fixed. In the bottom of the fixed box is a valve like the common bellows, and a pipe on the same level to let out the blast. The change of capacity, by the motion of this box, causes the blast, and with less waste of power than that occasioned by the bending of the leather in the common bellows. This advantage is, however, probably more than compensated by the loss of air from the box not fitting on the sides. See a description of this and some other blowing-machines under Pneumatics.

The common smith's bellows have latterly been constructed of a circular form. The boards of these bellows are bellows, round, and the movable boards parallel to the horizon and to each other. We have given a view of this construction in Plate CVIII. figures 4 and 5. A is the blast-pipe, B the movable lower board, C the fixed board, into which the pipe is inserted, and D the upper movable board, on which is placed a weight to regulate the strength of the blast. Motion is given to the lower board by the lever L, and the chain H working on the roller R.

The form of these bellows being cylindrical, the weight required to produce a certain pressure and strength of blast will be easily determined. If the diameter be one foot, the area will be 113-19 inches. The most convenient and pro- per blast for smith's bellows is about \( \frac{3}{4} \) lbs. upon the inch, or from that to \( \frac{1}{2} \) lbs. The upper board, in this case, would require a weight of 56-5 to give a blast equal to half a pound upon an inch. This pressure would give a velocity equal to about 207 feet in a second. If the diameter of the nose-pipe be changed, the number or length of the strokes, or both, must be changed, in order that the pressure and the corresponding density of the blast may remain the same. If the number and length of the strokes be kept up, and the aperture diminished, at the same time that the capacity of the bellows admits not of enlargement, the pressure and density of blast will be increased, although no additional weight be laid on. This frequently happens in the smith's bellows when he makes an increased effort to blow after the upper cavity is full. It is much better, however, not to exert the bellows in this way when a stronger blast is required, but to produce the effect by an additional weight. A very strong blast is found to be injurious to the iron when welding heats are required, and still more so in working steel. It is much better that an increase of air, which is frequently wanted, should be furnished by increasing the aperture, supposing the power to be at the time adequate to keep up the increased supply. Bellows should therefore be so constructed that the pressure may be uniform, and not immediately under the control of the workman. When he wishes to quicken his heat, he should have the means of increasing the aperture by a circular plate turning on an axis at right angles to the length of the pipe, as seen in fig. 9. When in the position \( ab \), the whole area is filled; when in that of \( cd \), the air passes in its full quantity. The index being placed at any intermediate points \( ef \), will let in any proportionate quantity required.

The aperture might be made to change, by the increase of power upon the machine, and thus caused to regulate itself. Several simple contrivances of this kind may be applied by any one skilled in machinery.

These improvements would render the common leather bellows, of the form above given, very useful for smiths. The irregular blast occasioned by their present construction is found to be very injurious to the iron, both as to its quality and economy. This is abundantly shown in the use of some blowing machines lately invented, which have the advantage of a blast that is uniform, and at the same time much softer, being produced by a small pressure.

These blowing machines are also found to answer very well for melting cast iron, the soft blast having less tendency to destroy the carbon, and the quantity of air being compensated by increasing the aperture.

One of these machines is the invention of Mr Street, for which he took out a patent. It consists of a barrel-shaped vessel, from four to five feet in diameter, and of a length more or less proportionate to the work it has to perform.

This cylinder is supported on two bearers by the two ends of its axis, like a barrel churn. The cylinder is divided into two equal parts by a plane in the direction of its length, fitting the two ends and the upper side, watertight, and extending downward to a small distance from the opposite side. This septum is in a perpendicular position when the cylinder is at rest. When this vessel is partly filled with water, and is made to pass through a certain space on its axis, the air which occupies the upper part of the vessel will be compressed on one side by the water, which flows from one side of the septum to the other, and will become in the same degree rarefied on the other, from a contrary cause. If, however, in this situation, a valve be made to open inwards from the atmosphere on the rarefied side, and another to open outwards on the condensed side, two equal and contrary currents will be established, one inwards and the other outwards. Blowing On the returning stroke both these valves will shut, and the other two sides will be put in the same situation with the first cavities. If, now, two similar valves to the last be introduced, two similar currents will be produced. If the two valves at which the air escapes from the machine, one on each side of the septum, be made to communicate with one cavity from which a nose-pipe proceeds, while the other two valves communicate with the atmosphere, every stroke will discharge a quantity of air through the nose-pipe from one cavity, and introduce the same volume of air from the atmosphere into the other cavity. These strokes are produced by the oscillating motion of the machine, the limit of its vibrations being about a quarter of the circle, or 90°.

These alternate puffs of air are first propelled into a vessel containing water to regulate the blast. This vessel is divided into two portions by a septum, which passes from the close cover at the top nearly to the bottom. When the air is forced into the cavity, which is close at the top, it expels the water under the septum at the bottom into the open cavity, so as to keep a constant head in the latter, compressing the air in the former. From this air-chest a nose-pipe proceeds to the fire, and the air escapes from it with a uniform velocity so long as the same column of water in the chest is preserved. This description answers to the first machine of the inventor; he has since taken out a second patent, the specification of which is given in the Repository of Arts, vol. xxviii., p. 193. We shall here give a description of this machine, with the patentee's improvements. See Plate CVIII. figs. 1, 2, and 3.

Fig. 1 is a longitudinal section of this machine. AB is the cylinder resting upon the axis \( ab \) and \( cd \), which are supported on the uprights \( gg \). The oscillating motion is given to it by a rod working upon the pivot \( p \), the other end of which is connected with a crank of such a length as to cause the cylinder to move through an arch of 90 degrees. The vessel is filled with water to the height \( ax \).

The part CBD (fig. 2) is cut off from the rest of the cylinder by two planes meeting at \( c \), and continuing down to the axis \( x \), so as to work upon its convex surface. These planes extend the whole length of the cylinder, and are then divided transversely into three cavities GHI, as seen in fig. 1. The cavity G is for the reception of the external air, and is called by the patentee a receiving box. The cavity H is open to the atmosphere, the periphery of the cylinder being removed in that part. The cavity I is appropriated to the air which is driven out of the machine, through the valves \( tt \) and \( gg \) (fig. 3), which open alternately on each side. The cavity G is divided longitudinally in the middle, forming two cavities \( m \) and \( n \), fig. 2; two valves, \( e \) and \( f \), fig. 1, open into each, one from the end of the cylinder, and the other from the cavity H. Each of the cavities \( m \) and \( n \) communicate with the body of the cylinder by the holes \( hh \) in the dividing planes. The cavity I has no division, as it receives the air from both sets of exit valves, which escapes at the pipe P.

The axis \( ae \) works within the axis \( ab \) and \( cd \), and is rendered air-tight by a stuffing-box within the latter. This axis will have the effect of remaining at rest while the cylinder is in motion, there being no other force exerted to turn it than the friction of the stuffing-box. The use of this axis is to support and turn a swing valve MV, which is made of rolled iron, strengthened by ribs connected with the axis. This valve is a plane, which would exactly sweep the interior surface of the cylinder without touching it. If the axis \( rz \) be held fast, the valve will retain its perpendicular position, while the cylinder performs its vibrating motion. The water would also remain at