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very large

Pneumatic expel it with this velocity. The weight of this column This table extends far beyond the limits of ordinary Pneumatic

is the least force that can be exerted by the engine : but use, very few blast-furnaces having a force exceeding Engines.
this force is too small to overcome the resistance in the 60 inches of water.
middle of the stroke, and it is too great even for the end We shall conclude this account of blowing machines
of the stroke, and much too great for the beginning of with a description of a small one for a blowpipe.
it. But if the machine is turned by a very heavy water- ABCD, fig. 100. is a vessel containing water, about Fig. 1Co.
wheel, this will act as a regulator, accumulating in it- two feet deep. EFGH is the air-bos of the blower
self the superfluous force during the too favourable posi- open below, and having a pipe ILK rising up from it
tions of the crank, and exerting it by its vis insita dur- to a convenient height; an arm ON which grasps this
ing the time of greatest effort. A force not greatly es- pipe carries the lamp N : the blowpipe LM comes from
ceeding the weight of this column of air will therefore the top of the upright pipe. PKQ is the feeding pipe
suffice. On the other hand, if the strength of the blast reaching near to the bottom of the vessel.
be determined, which is the general state of the problem, Water being poured into the vessel below, and its
this determines the degree of condensation of the air, cover being put oul, which fits the upright pipe, and
and the load on the square inch of the piston, or the touches two studs a, a, projecting from it, blow in a
mean force which the machine must exert on it. A

quantity of air by the feeding pipe PQ; this expels the
table, which will be given presently, determines the water from the air box, and occasions a pressure which
cubic feet of common air expelled in a second, corre- produces the blast through the blowpipe M.
sponding to this load, This combined with the proposed In N° 54. of this article, we mentioned an applica-
dimensions of the cylinder, will give the descent of the tion which has been made of Hero's fountain, at Chem-
piston or the length of the stroke.

nitz in Hungary, for raising water from the bottom of
These general observations apply to all forms of bel- a mine. We shall now give an account of this very in-
lows; and without a knowledge of them no person can genious contrivance.
erect a machine for working them without total uncer- In fig. 101. B represents the source of water elevated Fig. Icr.
tainty or servile imitation. In order, therefore, that they above the mouth of the pit 136 feet. From this there
may be useful to such as are not accustomed to the ma- is led a pipe B 6 CD four inches diameter. This pipe
nagement of even these simple formulæ, we insert the enters the top of a copper cylinder b c de, 8. feet high,
following short table of the velocity and quantity of air five feet diameter, and two inches thick, and it reaches
discharged from a cylinder whose piston is loaded with to within four inches of the bottom ; it has a cock at
the pounds contained in the first column on every square This cylinder has a cock at F, and
inch. The second column contains the velocity with one at E. From the top b c proceeds a pipe GHII
which the condensed air rushes out through any small two inches in diaineter, which goes down the pit 96
hole; and the third column is the cubic feet discharged feet, and is inserted into the top of another brass cy-
from a hole whose area is a square inch; column fourth linderf g hi, which is 6 feet high, four feet diameter,
contains the mean velocity of air of the common den- and two inches thick, containing 83 cubic feet, which is
sity; and columo fifth is the cubic feet of common air very nearly one half of the capacity of the other, viz.
discharged; the sixth column is the height in inches at of 170 cubic feet. There is another pipe NI of four
which the force of the blast would support a column of inches diameter, which rises from within four inches of
water if a pipe were inserted into the side of the cylin- the bottom of this lower cylinder, is soldered into its
der. This is an extremely proper addition to such ma- top, and rises to the trough NO, which carries off the
chines, showing at all times the power of the machines, water from the mouth of the pit. This lower cylinder
and teaching us what intensity of blast is employed for communicates at the bottom with the water L wbich
different purposes. The table is computed from the collects in the drains of the mine. A large cock K
supposition that the ordinary pressure of the air is 15 serves to admit or exclude this water; another cock M,
pouvds on a square inch. This is somewhat too great, at the top of this cylinder, communicates with the ex-
and therefore the velocities are a little too small; but ternal air.
the quantities discharged will be found about one-third Now suppose the cock C shut, and all the rest open ;
too great (without affecting the velocities) on account of the upper cylinder will contain air, and the lower cy-
the convergency of the stream.

linder will be filled with water, because it is sunk so

deep that its top is below the usual surface of the mine-

waters. Now shut the cocks F, E, M, K, and open
the cock C. Tlie water of the source B must run in

by the orifice D, and rise in the upper cylinder, com-
줄 239
1.72 14

pressing the air above it and along the pipe GHH', and
333 2.32 355 2.47 27

thus acting on the surface of the water in the lower 2.791 437 3.05 40

cylinder. It will therefore cause it to rise gradually 457 3.17 518 3.60 54

in the pipe IN, where it will always be of such a height 2 500 3.48 584 | 4.2 68

that its weight balances the elasticity of the compressed 3 544 | 3.76 653 4.53


air. Suppose no issue given to the air from the upper
31 582 4.03

715 4.98

cylinder, it would be compressed into one-fifth of its
611 4.24 774 5:38 109

bulk by the column of 136 feet high ; for a column of
642 4:46.822

34 feet nearly balances the ordinary elasticity of the air.
6664.67 888 6.17 136

Therefore, when there is an issue given to it through
si 693 4.84 950 6.49 150

the pipe GHH', it will drive the compressed air along
711 5.06 997 6.92 163
this pipe, and it will expel water from the lower cylin-


1.66 247

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I 22



Pneumatic der.

When the upper cylinder is full of water, there bullet. This rapid congelation is a remarkable instance Pneumatis Engines. will be 34 cubic feet of water expelled from the lower of the general fact, that air by suddenly expanding, ge- Fegins

cylinder. If the pipe IN had been more than 136 feet nerates cold, its capacity for heat being increased. Thus
long, the water would have risen 136 feet, being then the peasant cools his broth by blowing over the spoon,
in equilibrio with the water in the feeding pipe B b CD even from warm lungs : a stream of air from a pipe is
(as was shown in N° 52.), by the intervention of the always cooling.
elastic air ; but no more water would have been ex- The above account of the procedure in working this
pelled from the lower cylinder than what fills this pipe. engine shows that the efflux both at N and E becomes
But the pipe being only 96 feet high, the water will very slow near the end. It is found convenient therefore
be thrown out at N with a very great velocity. If it were not to wait for the complete discharges, but to turn the
not for the great obstructions which water and air must cocks when about 30 cubic feet of water have been dis-
meet within their passage along pipes, it would issue at N charged at N: more work is done in this way. A

with a velocity of more than 50 feet per second. Ittleman of great accuracy and knowledge of these subjects
issues much more slowly, and at last the upper cylinder took the trouble, at our desire, of noticing particularly
is full of water, and the water would enter the pipe GH the performance of the machine He observed that
and enter the lower cylinder, and without displacing the each stroke, as it may be called took up about three mi-
air in it, would rise through the discharging pipe iN, nutes and one-eighth; and that 32 cubic feet of water
and run off to waste. To prevent this there hangs in were discharged at N, and 66 were expended at E. The
the pipe HG a cork ball or double cone, by a brass expence therefore is 66 teet of water falling 126 feet,
wire which is guided by holes in two cross pieces in the and the performance is 32 raised 96, and they are in
pipe HG. When the upper cylinder is filled with water, the proportion of 66x136 to 32 x 96, or of i to
this cork plugs up the orifice G, and no water is wasted; 0.3422, or nearly as 3 to 1. This is superior to the
the influx at D now stops. But the lower cylinder con- performance of the most perfect undershot mill, even
tains compressed air, which would balance water in a when all friction and irregular obstructions are neglect-
discharging pipe 136 feet high, whereas IN is only 96. ed; and is not much inferior to any overshot pump-mill
Therefore the water will continue to flow at N till the that bas yet been erected. When we reflect on the
air has so far expanded as to balance only 96 feet of great obstructions which water meets with in its passage
water, that is, till it occupies one-fourth of its ordinary through long pipes, we may be assured that, by dou-
bulk, that is, one-fourth of the capacity of the upper cy- bling the size of the feeder and discharger, the perfor-
Jinder, or 42.5 cubic feet. Therefore 42 cubic feet mance of the machine will be greatly improved; we do
will be expelled, and the efflux at N will cease; and the not hesitate to say, that it woud be increased one-
lower cylinder is about one half full of water. When third : it is true that it will expend more water ; but
the attending workman observes this, he shuts the cock this will not be nearly in the same proportion ; for most
C. He might have done this before, had he known of the deficiency of the machine arises from the needless
when the orifice G was stopped; but no loss ensues velocity of the first efflux at N. The discharging pipe
from the delay. At the same time the attendant opens ought to be 110 feet high, and not give sensibly less water.
the cock E, the water issues with great violence, being Then it must be considered bow inferior in original
pressed by the condensed air from the lower cylinder. expence this simple machine must be to a mill of any
It therefore issues with the sum of its own weight and kind which would raise 10 cubic feet 96 feet high in a
of this compression. These gradually decrease together, minute, and how small the repairs on it need be, when
by the efflux of the water and the expansion of the air; coni pared with a mill.
but this efflux stops before all the water has flowed out: And, lastly, let it be noticed, that such a machine can
for there is 424 feet of the lower cylinder occupied by be used where no mill whatever can be put in motion.
air. This quantity of water remains, therefore, in the A small stream of water, which would not move any
upper cylinder nearly : the workman knows this, be- kind of wheel, will here raise one-third of its own quan-
cause the discharged water is received first of all into tity to the same height; working as fast as it is supplied.
a vessel containing three-fourths of the capacity of the For all these reasons, we think that the Hungarian
upper cylinder. Whenever this is filled, the attendant machine eminently deserves the attention of mathemati-
opens the cock K by a long rod which goes down cians and engineers, to bring it to its utmost perfection,
the shaft; this allows the water of the mine to fill the and into general use. There are situations where this
lower cylinder, allows the air to get into the upper cy- kind of machine may be very useful. Thus, where the
Jinder, and this allows the remaining water to run out tide rises 17 feet, it may be used for compressing air to
of it.

seven-eighths of its bulk; and a pipe leading from a And thus every thing is brought into its first condi- very large vessel inverted in it, may be used for raising tion; and when the attendant sees no more water come the water from a vessel of one eighth of its capacity 17 out at E, be shuts the cocks E and M, and opens the feet high; or if this vessel has only to of the capacity cock C, and the operation is repeated.

of the large one set in the tide way, two pipes may be led There is a very surprising appearance in the working from it, one into the small vessel and the other into an equal of this engine. When the efflux at N has stopped, if vessel 16 feet higher, which receives the water from the the cock F be opened, the water and air rush out toge- first. Thus one sixteenth of the water may be raised 34 ther with prodigious violence, and the drops of water feet, and a smaller quantity to a still greater beight; and are changed into hail or lumps of ice. It is a sight this with a kind of power that can hardly be applied in usually shown to strangers, who are desired to hold their any other way. Machines of this kind are described hats to receive the blast of air: the ice comes out with by Schottus, Sturmius, Leupold, and other old writers; such violence as frequently to pierce the hat like a pistol and they should not be forgotten, because opportunities



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