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illuftrated by a Rgure, (fee Plate XIII. Pneuma.'h-SyJ^^. lo?-.) 

 in which tlie out:r box ABCPFE has its top and two 

 fides flat or ftraight, and the end BAEf formed into an 

 Evchcd or cyHndrical furface, of wliich the h!ne FP at the 

 other end is the axis. This box ii open below, and receives 

 within it the iliallow box KHGNiML fj-rr, 109.) which 

 exaaly iilla it. The line FP of the one coincides with FP 

 of the other, and along this line is a fct of hinges on which 

 the upper box turns, as it rifes and finks. The lower box 

 is falleiied to a frame fixed in the ground. A pipe OQ^ pro- 

 ceeds from the end of it, and terminates at the furnace, in 

 a fm?.ll pipe called the " tewer," or " tuyere." This lower 

 box is open above, and has in its bottom two large valves 

 V,V, opening inwards. (See^ir. 110.) The condnfiting pipe 

 is fometiracs furnifticd with a valve opening outwards, to 

 prevent burning coals from being fucked into the bellowp, 

 when the upper box is drawn up. Tjje joint along PF is 

 made tight by thin leather nniled along it. The fides and 

 ends of the fixed box are made to fit the fides and curved end 

 of the upper box, lo that this lall can be railed and lowered 

 round the joint FP without fenfible friftion, and yet with- 

 out fuffering much air to efcape ; but as this would not be 

 fui^icitntly air-ti^ht by reafon of the (hrniking and warping 

 of the wood, a further contrivance is adopted. A (lender 

 lath of wood, divided into feveral joints, and covered on the 

 outer edge with very folt leather, is laid along the upper 

 edges of the fides and ends of the lower box. This lath is 

 fo broad, that when its inner edge is even with the infide of 

 the box, its outer edge projects about an inch. It is kept 

 in this pofition by a number of fteel wires, which are driven 

 into the bottom of the box, and Hand up, touching the fides, 

 as reprefented in Jig. 1 1 1, where a i c are the wires, and e 

 the lath, prcjefting over the outfide of the box. By this 

 contrivance, the laths are prelTcd clofe to the fides and 

 curved end of the moveable box, and the fpring wires yield to 

 all their inequalities. A bar of wood RS fjig. 108.) is fixed 

 to the uppjr board, by which it is either railed by machinery, 

 to fink again by its own weight, having an additional load on 

 it, or it is forced downward by a crank or wiper of the ma- 

 chinery, and afterwards raifed. The operation, in this cafe, 

 is exaftly fimilar to that of blowing with the chamber bel- 

 lows. When the board is lifted up, the air enters by the 

 valves V,V, f^. no.) and is expelled at the pipe OQj by de- 

 preffing the boards. Thcfe bellows are made ot a very great 

 lize, AD ([fig.ioS.) being 16 feet, AB 5 feet, and the circular 

 end alfo 5 tect. The rife, however, is but about 3 or 3-!- ftet. 

 They expel at each ftroke about 90 cubic feet of air, and 

 make about 8 ilrokes per minute. The advantages of thefe 

 wooden bellows are very confiderable. When they are 

 made of clean fir wood without knots, they wilt lad 30 or 

 40 years, and even longer, though continually kept in aftion 

 46 or 48 weeks every year. Some have faid, that, when pro- 

 perly made, they will lad a century. The effeft produced 

 by them is ftronger, as well as more uniform, and can be 

 moderated according to circumflances. They are worked 

 alfo with greater facility. The flips of wood on their fides 

 are apt to be damaged ; but they can foon and eafily be 

 repaired. Every three or four months, however, the outer 

 fides only of the inner box, and the bolt which keeps the * 

 bo-xcs together, mull be fmeared with oil. If we calculate 

 the price of fuch bellows, and the yearly expcnce, they will, 

 according to Grignon's account (ubi fupra) be only a fifth 

 part of thofe of the old leather bellows. They have, in- 

 deed, their defefts, though they are kfs expenfive and more 

 durable than thofe qf leather ; for it is fcnrcely pofTible to 

 make the jundlures fo tight as to allow no exit to the com- 

 prefl'ed air, and the friftion mull neceflarily be very great, 

 iome, therefore, have had recQurie to wutcr, for performing 

 Vol. IV. 



BEL 



the office of the lower board of the bellows. A bellows oa 

 this principle is defcribed by Mr. Treiwald, engineer to liij 

 Svvedifh m<ijefty, in the Pnilofophical Trufaciions, under 

 the name of a " water-bellowsr." Of bellows of wood wc 

 have one preferved in the repofitory of the Royal Society ; 

 and Dr. Plot defcribcs another, that was ufed at the copper- 

 works at EllaRon in Staffordiliire. Nat. Hill. Staff, ch.iv.ij 18. 

 Such are tlie bellows in general ufe on the continent. In this 

 kirgdom, a dilierent, and a preferable form is adopted ; for 

 an account of which, and other contrivances for animating 

 the large fires of Turnaces, &c. fee Blowing Machine. 

 See alfo Furnace. 



Bellows, ^/>of//9/i/;/V, fo called by the inventor M. Gorcr, 

 phyfician to the militarj- hofpital at Neufbrifack, and denot- 

 ing " reflorcr of refpiration," an inllrument ufed for infla- 

 ting the lungs. It is defcribed in the " Journal de Medi- 

 cine" for June 1789 ; and confifts of a double pair of bel- 

 lows BCLM {P/iite XIU. Piinimalks,fo. 112.) the two 

 dificrent parts of which have no communication with each 

 other. In the lower fide BM is an aperture A for a valve, 

 conftrufted on the principles of thofe of Mr. Nairnc's air- 

 pump. It confills of a rim of copper, clofed at one end 

 by a plate of the fame metal, in which plate are feven fmall 

 holes placed at equal diftances. This plate is covered with 

 a piece of filk coated with eladic gum, in wliich are fix 

 tranfverfe incifions of two or three lines in length. Each. 

 incifion is fo made as to be fituated between two of the 

 holes, and at an equal diftance from each, as reprefented at D, 

 (Jli;. 113). The filk mull be made very fecure, by a thread 

 palfing feveral times round the rim. It is obvious, that a 

 ftream of air applied to that fide of the plate which is op- 

 pofite the filk, will pafs through the holes, and, lifting up 

 the filk, efcape through the incifions. On the contrary, a 

 flream of air applied to the other fide will prefs the filk 

 upon the plate, and thus clofe the holes, fo that it will be 

 impofiible for it to pafs through them. This valve opens 

 internally, fo as to admit the air from without. At B is 

 another valve, upon the fame conftruftion, but opening in 

 a contmi-y direftion, thus permitting the air to efcape out 

 of the lower part into the tube EF, but preventing its en- 

 trance. At C is another valve, opening internally to ad- 

 mit the air from the tube EF ; and at D there is a fourth, 

 opening externally to difcharge tlie air from the upper part. 

 The flexible tube EF, fcrevved on at the end CB, being in- 

 troduced into one of the noftrils, whilfl the mouth and the 

 other nollril are clofed by an afiiflant, if we feparate the 

 two handles L, M, which were clofe together at the intro- 

 dutlion of the tube, it is evident, that the air in the lungs 

 will rufli into the upper part through the valve C, whilft 

 the external air will fill the lower part through the valve A. 

 The two handles being again brought into contafl, the at- 

 mofpheric air will be forced into the lungs through the valve 

 B, and at the fame time the air in the upper part will be 

 difcharged at the valve D. Thus, by the alternate play of 

 the double bellows, the lungs will be alternately filled and 

 emptied as in refpiration. In ufing the inllrument, care 

 (hould be taken not to be too violent ; as the more per- 

 feftly the natural motion of refpiration is imitated, the better. 

 To prevent any fubllances from without injuring the valvtl 

 A, D, (fg. 112.) the rim is made with a fcrcw B, (Jig. 114.') 

 in order to receive a cap A, A, (fg. 114.) full of (mail 

 holes. This fcrew has alfo another ufe. if dephlogidi- 

 cated air be preferred, a bladder filled with it Cfig.HS-) 

 may, by means of the fcrew A, be fadened to the valve A, 

 (fig. 1 1 2.) ; and to prevent wade, as this air may ferve feve- 

 ral times, a flexible tube may be fcrewed in the valve D, 

 (fig. 112.) communicating with the bladdtr by means of 

 the opening d, (fg. 115). Tlius it may be employed a« 



Y often 



