BLOWINO-MACHIN1X 



MACHINES. 





thr vapour of tbt vulatiliaod alkali. PoUih ooloun the flam* violet ; 

 Ihhia. rod ; and soda, yellow. The colouring power of nod* being 

 much greater than that of potash, a mixture of the two shows the 

 traction for soda. Bat if euoh a flame be looked at through a violet- 

 coloured glass, the yellow light of the aoda flame u absorbed, and the 

 violet colour of the potaadum u teen, eren if only a amall quantity of 



. . -... 



MeUlUo tin U employed with difficultly reducible metal* ; ita wy 

 f.uibilHy bring, it in contact with the metallic oxide., and aaabto in 



Nitrate of potaah U used to effect the oxidation of those metals, 

 t higher oxide* furnish oharacterwtM compound* with the alkali. 



Thus aa oxide of chromium heated with nitrate of potaah before the 

 blow-pipe, yield* ehramato of potaah ; a yellow aalt in which the 

 chromic acid can be eaaily detected. Manganese furnishes, when heated 

 with nitrate of potaah and carbonate of aoda, a characteristically green- 

 ooloured manffuiate of nnt*i 



v E8 are contrivance, for producing a current 

 ( air for the purpose of exciting the requisite intenaity of combustion 



for BMtallurgioal and 



require great heat The 



thnpler kind* are described under BILLOWS ; but the larger and more 

 omnplei varieties are here noticed. 



It will be remembered that the t*'<V<*r implement, bellows, con- 

 wU of an air-tight chamber of variable dimensions, having one 

 aperture doted by a valve which can only open inward*, and another, 

 which i* connected either directly or indirectly with the nozzle, or 

 jiipe for the exit of the current of air, cloaed by a valve which can only 

 pen outward*. When, by the application of mechanical force, this 

 chamber i* ditUnded or enlarged, the pressure of the external air 

 open* the valve which open* inwards, and consequently the chamber 

 become* filled with air ; but when, by an altered application of power, 

 the chamber i* compressed as to reduce its capacity, the con- 

 dentation of the included air causes the valve by which it entered to 

 dose, and that which open* outward* to open, so that the air escape* 

 by the nonle, with a degree of force and rapidity proportionate to the 

 |*ttur* employed in compressing the chamber. The leathern bag of 

 the musical instrument called a bagpipe ia an example of such a 

 variable, or expansible and compressible, chamber, and would therefore, 

 if fitted with a nozzle, form a substitute for the common domestic 

 bellow* ; but the tame effect is produced, in a much more con . 

 way, by the use of a chamber formed of two boards, the edges of which 

 are connected by pieces of leather kid in folds in such a manner that 

 the upper board may be raised or depressed at pleasure, while the 

 lower board remains stationary. 



The blast produced by such a machine as has been described is 

 intermittent, and also variable in intensity. The first of these defects 

 may I* remedied by employing two separate bellows or pairs of 

 bellows, worked alternately, so that the one may be expelling air 

 while the other U drawing in a fresh supply. While, however, the 

 blast this* produced is continuous, it is by no means equable in force. 

 To remedy thi* defect the air expelled from the chamber already 

 described should be forced into a second chamber, like it, of variable 

 dimension*, but compressed by a weight so as to produce a constant 

 (bad/ pressure; and the nozzle should be made to open into the 

 teond dumber. In forge-bellow* of this construction there are three 

 board*, connected by leather aide* which are kept in regular folds by 

 hoop* of eane. The middle board i* fixed in a horizontal position, and 

 bat the nozzle attached to it, while the upper and lower boards are 

 moveable, and are loaded with weight*; the effect of which is that 

 when the machine is at rest the chamber formed between the upper 

 and the middle boards ia collapsed, while that between the middle and 

 tke lower board, i* distended and full of air. When in use the lower 

 board ia raised by mean* of a lever and chain, and the air enclosed 

 between it and the middle board i* forced through a valve into the 

 upper chamber; and by the rapid repetition of thin action the upper 

 chamber it filled with air more rapidly than the nozzle can carry it off, 

 o that the upper board rite*. The working of the bellows may i 

 Winded for a time ; teeing that a continuou* and equable blast will be 

 maintained by the prearare of the loaded upper board until it lias, by 

 the complete expulsion of the air, descended to ita original position. 

 It thould be remembemd Uut thi* perfect equability of Hart i only 

 "Mhltahied while the working of Uw bellow* ia *u*pended, became 



loaded board ; while, during the working of the bellows, the pressure 

 alternate, between that and the superior pressure produced by the 

 iooux of air from the lower chamber, thereby causing the upper board 

 to rW and fall with each stroke. Many nrniths 1 bellows are made of 

 the pear-ahaped form common to hand bellow., and have the board*, 

 or at leatt the lower and middle board*, united by a kind of hinge- 

 joint; but the superior machine* of thi* description have the board* 

 circular , and the working apparatu* so arranged a* to make their 

 !*" V**'. * ta *.. far portable forge., helical 



ar. applied to the boards in lieu of weights. 



Beckmam, C History of InvwtionsTob* 

 a* were formerly used in nmelUng-li 



I iprings 



. observe* that large bellow*, 

 melting-hooM*, when made with 

 attended with many inconvenience*. .They require 

 MH*gm*rt tad expensive repair*, and wear out after a few 

 need* to be frequently greased or oiled, in 



order, if it be thin, to prevent the enclosed air from passing through 

 it, or, if thick, to keep the leather *oft and pliable, and prevent it 

 from cracking in the folds. These defect* led to the invention, 

 apparently in Germany, in the 10th or 17th centurv, of bellow, formed 

 entirely (excepting the nozzle and ainu. .vood; these were 



long used in metallurgic operation* uc nt, and appear, from 



what Beckmann says as to their i-ii; be well adapted for use 



where more perfect machines are unattainable. Tin- annexed cut, 

 representing a side elevation of such an apparatus, will sufficiently 

 explain the structure of wooden bellows. In this figure a represents 

 a wooden box of an oblong square form, the upper edge of !, 

 indicated by dotted lines. It is open at tin- toji, and from <>no end .if it 

 proceeds the nozzle 4, which, as well as the bottom board of the box, U 

 supplied with a flap-valve, like common bellows. This box in fix. 

 horizontal position, and is covered by the box r, which is OJM-H at the 

 bottom, and is so much larger than a as to allow ita sides to >'. 



and down outside the sides of the lower box without actual contact. 

 The two boxes are united at the nozzle end by a hinge-joint formed 

 by the bolt </, and the upper box is capable of being worked up and 

 down by the projecting handle e. Great friction would be occasioned 

 if an attempt were made to obtain a close fit by the accurate adjust- 

 ment of the boxes one to the other ; and it would be impossible, in 

 consequence of the shrinking and warping of the wood, to make the 

 machine air-tight; but this difficulty is obviated by attaching thin 

 slips of wood to the inner sides of the box e in such a manner an t . i ill 

 up the space between the two boxes : such slips being rendered r\- 

 flexible by cutting them nearly through with a saw at interv 

 fifteen or eighteen inches, and by being pressed into close contact with 

 the sides of the box a by small metal springs. The same object might 

 be readily effected by slips of leather. Wooden bellows of this con- 

 struction are both cheap and exceedingly duralile. tin- clip- or laths 

 which render them air-tight being the only part liable to wear ; and 

 these are easily replaced. Though we find no notice of such a modi- 

 fication of them, a very trifling exercise of ingenuity would lie suil 

 to form double bellows of this simple character. The HOY. John 

 Williams, when serving his life of usefulness as a missionary in the 

 South Sea Islands, taught the natives how to make a blowing-machine. 

 This apparatus, invented by him in the absence of any available 

 information respecting such contrivances, consisted of two square 

 boxes containing pistons that were alternately raised by levers, and 

 suffered to fall by their weight, aided by a load of stones; the whole 

 forming a rude imitation rather of the cylinder blowing-engines now 

 used in iron- works, than of common bell' 



A very different kind of blowing-machine, which appears to be of 

 French origin, and has been much used for blast-furnaces on the 

 Continent, and also, we believe, in the United States of North America, 

 though it does not appear to have been much adopted in this country, 

 U the water blowing-engine, otherwise called trombe or iron 

 which water is allowed to fall in a minutely divided stream by pi rring 

 through a colander, or by some other contrivance, down a large tube 

 in the sides of which, near the upper end, are several apertures for the 

 admission of air. In so falling the water draw* with it a great quantity 

 of air, which passes with it into a vessel at the bottom of the ),i],.-. 

 where the water dashes upon a pedestal which disperse* it through 

 the vessel By this action the separation of the air and water appears 

 to be facilitated ; and consequently the nil the upper part of 



the vessel, whence it is conducted by a pine to the furnace ; while the 

 water escape* by apertures provided for the purpone in the lower part 

 of the vessel. The action of thi* kind of >! .-. which i, 



represented in several different forms, has been variously explained l-y 

 different writers ; the powerful current of air produced by it lias been 

 compared to the wind whi. h accompanies violent showers of rain. It 

 i* worthy of remark, as probn' ; it- UJUIIP, if 



not also of the invention of this apparatus, that itx French name 

 trombe u the same as that of the meteorological ]!.. n o.. ;>..n which we 

 call a water-spout. 



The great improvement* which have been effected in the iron manu- 

 facture within the last century are, in a great measure, due to the 

 introduction of very powerful blowing-machines, in which the air is 

 alternately drawn into and expelled from large cylinders, resembling 

 thoae of a (team-engine, by the action of pistons impelled by a con- 

 nection with water-wheel* or steam-engine*. The finrt blowing- 

 machine, or force-pump* of thi* character on a large scale were those 

 of the Carron foundry, constructed by Smeaton, and set to work in the 

 year 1760. The arrangement of the piston and valve* i* so similar to 

 that of a steam-engine cylinder as to need no detailed description. In 



