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tenor of tVie cKeft, a fimilar height. Tliis defcription takes 

 it for granted, that the fpaccs C C are equal to the area of 

 the inverted cliell ; fo that every inch of water forced out 

 of the cheft adds exaftly one inch to the height of the 

 coUimn. 



A blowing maclcine, capable of blowing to purpofe two 

 blaft furnaces, ought to liave the inverted chell of the regu- 

 lator equal to three or four hundred fquare feet of area. 

 There cannot arife any error from having this large enough ; 

 the want of fpace and capacity frequently proves a real de- 

 triment. 



In calculating the proportions and dimenfions of water 

 regulators in general, the principle is, to allow the fpace 

 around the inverted chell equal in point of fiipevficial mea- 

 furemcnt to the area of the interior of the chdf , that the 

 defcending column of water may difplace no more in the 

 perpendicular afcent, than it is itfe't abfolutely deprelled. 



If the area or fpace, in which the water rifes and falls, 

 is only equal to half the area of the inverted cheft, then for 

 every foot of water which is depreifed in the bottom of the 

 cheft, a column of two feet will be raifed and maintained on 

 the outfide. On the contrary, if the outfide fpace for 

 water be equal to twice the area, then every foot of water 

 deprefled in the cheft will only elevate the external column 

 fix inches. 



It will appear evident from thefe general fafts, that a 

 confiderable latitude may at any time be afTumed in con- 

 ftrufting the water regulator, particularly in old eftabliihed 

 ■works, where local circumftances and conveniency confine 

 its fituation to one fpot. 



Where it is not inconvenient to ufe a high perpendicular 

 column of water, the inverted cheft may be increafed one 

 half, double, or even triple the fuperficial meafurement of 

 the outfide fpace ; fo that if the power of the blowing ma- 

 chine is equal to 3 lbs. upon the fquare inch, the water in 

 the cheft will be depreffed 3I feet nearly, and raifed in the 

 perpendicular column 5 feet j inches in the firft, 7 feet in 

 the fecond, and lOj feet in the laft cafe. This plan to fuit 

 former eftablifliments may be adopted with confiderable mo- 

 difications, always keeping in mind, that every foot of area 

 gained upon the furface of the water is a material acquifition 

 to the equalizing powers of the regulator. 



One imperfection attends this want of equilibrium on the 

 two fpaces for the aftion and re-attion of the water. — 

 \Vhatever fpace the waters would fall, at the return of the 

 ftroke, fuppofing the infide and outfide columns exaftly ba- 

 lanced, would in this cafe be increafed one half, double, or 

 triple. 



Again, where fituation does not admit of the perpendi- 

 tular column being raifed beyond, or not even to the extent 

 of the depreftion, that takes place within the inverted chelt, 

 and where an additional fpace cannot be procured for an in- 

 creafe of its diameter, an inverted chell of much lefs 

 height than common may be ufed, loaded with a material 

 cf great weight, fiich as iron. The water in that cafe would 

 diftribute itfelf over the furface of the cheil, inilead of 

 rifing in perpendicular height. 



One ferious objeAion, however, is made to chefts or cy- 

 linders, where the eduftiou pipe approaches within a fhort 

 fpace of the furface of the water ; namely, water rifing in 

 the pipes, and being conveyed along with the air into the 

 furnace. This may take place in two ways ; by an Infenfible 

 and uniform difcharge of water into the furnace, making 

 the blaft at the tuyere vifible, like the refpiration of the 

 human body in a frofty day ; or in quantity, threatening 

 utter deftruftion to the furnace and buildings. The former 

 ii occaiioned by the air from the edudion pipe> at the com- 



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men«ement of the ftroke, impinging violently upon the fur- 

 face of the vvaljtr, and raifing a portion of it in the ftate of 

 fpray. This is fpeedily diffolved or entangled in the mafs of 

 condenfed air before the return of the next ftroke, and be- 

 comes expreficd along with the blall into the furnace. The 

 other hazardous confequence is occafioncd chiefly by undu- 

 lation in the column of water, when the blowing machine is, 

 by derangement or accident, working under its proper 

 power or number of ftrokes. In thefe cafes, when the 

 paufe at the end of the ftroke is prolonged, an exhauf- 

 tion fometimes takes place iu the air-pipes, the water rifes 

 and is carried in a ftrcam through the blow-pipe into the 

 furnace. 



The fame cafualties may more readily occur, if the fur- 

 face of the water is upon a level, or nearly fo, with the 

 tuyere. 



In judicious ereftions this is mod carefully avoided ; the 

 furface of water in the inverted cheft or cyhnder is kept at 

 leaft S, 9, and 10 feet under the level of the tuyere, even at 

 the laft period of return, when the water has rifen to its 

 greateft height within. 



• This very proper precaution enfures an advantage of much 

 importance. A large fpace is obtained betwixt the top of 

 the cheft and the deprelled furface of the water ; this be- 

 comes a fpacious refervoir for the condenfed air, and, by ge- 

 nerating a confiderable portion of elafticity, prevents any 

 violent perturbation upon the water at any period of the 

 ftroke. The increafed diftance betwixt the furface of the 

 water, and the pipe which conducts the air from the cy- 

 hnder, has a complete tendency to prevent the elevation of 

 the aqueous particles, and always enfures a quantity of air 

 comparatively free from moifture. 



Upon the principles formerly noticed, it is poffible to con- 

 ftrudl a blowing apparatus of this nature, wherein there 

 could be little or no vifible motion in the perpendicular co- 

 lumn of water even with the fame engine. 



Let us fuppofe a machine of this nature at work, with an 

 accurately balanced column of water, the fall of which, at 

 the return of the ftroke, was equal to 12 inches. It is evi- 

 dent, that if the outfide fpace was enlarged fo much over its 

 furface as to contain this foot of water, without adding any 

 perceptible height to the column ; that included within the 

 cheft would, at the return of the ftroke, being fed from 

 a more capacious limlj, rife a foot, without any fenfible di- 

 minution taking place in the perpendicular height of the 

 external fluid. It is equally obvious, in this as in every 

 cafe with water regulators, that the rife and fall of the in- 

 fide column of water will remain the fame, under every mo- 

 dification and form, while the pace and powers of the engine 

 remain the fame. 



The application of water regulators to blowing machines 

 was foon followed by an attempt to further improvement, 

 by the introduttion of the air-vault ; tlie principle of which 

 was to form a receiver of fuch capacity, that the elafticity 

 or fpring of the condenfed air would be fufficient to ex- 

 prefs and cquaUze the blaft during the return of the 

 ftroke. 



To eff"eft this, an immenfe magazine was requifite ; to 

 ereft which of any metallic fubllance would have been 

 ruinoufly expenfive, and, if conftrufted of wood, infuffi- 

 cient for retaining the air. It became therefore i-equifite 

 to try the experiment upon building, or by excavation from 

 the folid rock. In both thefe ways has the air-vault been 

 tried, and found to produce an excellent eff^eft, as to 

 equahzing the denfity of the blaft ; but it has been con- 

 ceived with fuch indifferent confequenccs as to quantity, 

 that the plan is for the prefeut given up. 



Ail. 



