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breadth of the boiler, and at about twelve inches diftance 

 from one another. Thefe are placed twenty-four inches 

 above the furface of the fire. On thefe malfy bars of iron 

 they lay, crofs-wife, the common flat bars of iron, as eiofe 

 as they can lie t gether, and then make up the fides with 

 brick-work. In the middle of the bottom of this boiler is 

 laid a troui^h of lead, wherein they put at firft about a hun- 

 dred pound vi'cight of the rock. They ufe NewcaiUe coals 

 in the boiling; and if they find the liqr.or not ftronjr 

 enough, they add more of the rock at times, as it boils. 

 Phil. Tranf. N'' 142. 



The boiler for makinj; colours. Sic. muft: be made of pew- 

 ter ; becaufe iron and copper will be corroded by the ialine 

 fubllances ufed in the maniifafturv- of them. 



Count Rumford (See his Effays, vol. i. p. 220.) recom- 

 mends double bottoms to boilers, and alfo to faucepans and 

 kettles of all kinds, ufed for culinary piirpofes ; which con- 

 trivance, he fays, will, in all cafes, mod eflfedt'ially prevent 

 what is called by the cooks, " burning-to." The heat is 

 fo much obllruttcd in its paffage through the thin fheet of 

 air which, notwithllanding all the care that is taken to 

 bring the two bottoms into aftual contaft, will ftill remain 

 between them, that the fecond has time to give its heat as 

 fall as it receives it to the fluid in the boiler ; and confe- 

 quently it never requires a degree of heat fuffii-ient for burn- 

 ing any thing tliat may be upon it. He fuggefts that it 

 ■will probably be bell to double copper faucepans and fniail 

 kettles throughout ; and as this may and ought to be done 

 with a very thin fheet of metal, it would not coll much, even 

 if the lining were to be made of filver. When the two 

 fheets of metril that form the double bottoms of boilers are 

 made to toi'c'i each other throughout, by hammering them 

 together after the falle bottom has been fixed in its place, 

 they may be tacked together by a f-w fmall rivets placed 

 here and there, at cor.fiderable diltances from each other ; 

 and when this is done, the boiler may be tinned. In this 

 operation, if proper care be taken, the edge of the falfe 

 bottom may be foldered by the tin to the fides of the boiler, 

 and thus the water or other liquids, put into the boiler, will 

 be prevented from getting between the two bottoms. The 

 Count adds, that this invention of double bottoms might 

 be ufed with great fuccefs by ditlilers, to prevent their li- 

 quor, when it is thick, from burning to the bottom of their 

 flills. (See Still.) Having found in the courfe of his 

 experiments, (See Phil. Tranl. 1792, Part I.) that con- 

 fined air is the bell barrier that can be oppnfcd to heat for 

 the purpofe of confining it, he propofcd to confine the heat 

 in the boilers of his conftrudlion, and to prevent its 

 efcape into the atm^fphere, by means of double covers. 

 Thefe covers were made of tin, or rather of thin iron-plates 

 tinned, in the form of a hoUow-cone ; the height of the cone 

 being equal to about one-third of its diameter ; and thus the 

 air which it contained was entirely (hut up, the bottom of 

 the cone being clofcd by a circular plate or thin Iheet of 

 tinned iron. The bottom of the cone was accurately fitted 

 to the top of the boiler, which it completely clofed by means 

 of a rim about two inches wide, which entered the boiler ; 

 which rim was foldered to the flat (heet of tinned iron that 

 formed the bottom of the cover. The fleam, generated by 

 the boiling liquid, was carried off by a tube about half an 

 inch in diameter, which paffed through the hollow conical 

 cover, and which was attached to the cover, both above and 

 below, with folder, in fuch a manner that the air with which 

 the hollow cone was filled remained completely confined, and 

 cut off from all communication with the external air of the 

 atmofphere, as well as with the ileam it ger.erated in the 

 boiler. For his various contrivances in the moil advan- 



tageous conflruflion of boilers for the faving of fuel, and for 

 producing the defired effeft, we refer to his Effays, vol. ii. 

 p. iS, &c. 



BOILERY, or CoiLARY, in the Sn// IVorls, denotes a 

 falthonfe, pit, or other place, where fait is made. 



BOILING OF Meat, in Coohsry, is the expofing of 

 meat to the heat of boiling water, while it is immerfed in it 

 for a certain time. By this joint application of heat and 

 moidure, the texture is rendered more tender and more fo- 

 luble in the llomach ; and it is only in this way, that the 

 firmer parts, as the tendinous, ligamentous, and membranous 

 pnrts can be dulv foftened, and their gelatinous fubftance 

 duly cxtrafted. A moderate boiling rendero the texture of 

 animal flefh more tender, without much diminution of its 

 nutritious quality ; but if the boiling is extended to extradt 

 every thing foluble, the fubftance remaining becomes lefs 

 foluble in the flomach, and at the fame time much lefs nu- 

 tritious. But as boiling extrafts in the firfl place the more 

 foluble, and therefore the faline parts ; fo the remainder, 

 after boiling, is in proportion to the continuance of the 

 operation lefs alkalcfcent, and lefs heating to the fyflem. 



Boihng is commonly praftifed in open velTels, or in vcffels 

 not clofely covered ; but it may be performed in digefters, 

 or veffels accurately and tightly clofed ; and in fr.ch veffels 

 the effiCls are very different from thofe that take place in 

 open veffels. As we can hardly employ any other degree 

 of heat than that of boiling water, the water in the digefler 

 is never made to boil, lo there is no exhalation of volatile 

 parts ; and, although the folution is made with great fuc- 

 cefs, and may be to any degree required, yet if it be not 

 carried very far, the meat may be rendered very tender, 

 while it flill retains its mofl fapid parts ; and this kind of 

 cookery will always give the moll defirable ftate of boiled 

 meat. Boiling, in the ordinary way, is different, according 

 to the proportion of water that is applied. It a fmall quan- 

 tity be applied, and the heat in a moderate degree is conti- 

 nued for a long time, this is called " flewing," and has the 

 effedt of rendering the texture more tender, without ex- 

 trafting much of the foluble parts ; and of courfe it leaves 

 the meat more fapid, aud fufficiently nourifhing. CuUen's 

 Mat. Med. vol. i. p. 400, &c. 



Boiling, elulUtion, in Phfjics, is the internal commo- 

 tii.n excited in a mafs of water or other liquefied fubftance, 

 by the fucceffive convtrfion of the lower portions of the 

 fluid into vapour, and their violent effort under this expan- 

 five and elallic form to make their efcape. It is ufually, 

 though not neceflanly, produced by the application of heat. 

 The cir umllances which precede or accompany the pheno- 

 menon of boiling, arc beftobferved in a thin tranfparent flafli 

 nearly filled with water, and fufpendea over a lamp or a 

 charcoal fire. Numerous minute globules are fcen coUefting' 

 from all pohits towards the fides and rifing in a ftream to the 

 furface ; occafioned evidently by the difcharge of air, which 

 is always in fonie .proportion combined with water. As the 

 heat increafes, the liquid particles near the bottom of the 

 flafli fnddenly burft into fteam, and fhoot upwards ; but in 

 afcending through the colder mafs, they again collapfe, flop- 

 their prognfs-, and feem loft. Such alternate expanfions 

 and contraftions, by throwing the fluid into a gentle tremor, 

 frequently caufes a peculiar fort of finging noife, which is 

 rightly fuppofed to betoken the approach of acT:ual boiling. 

 This finging is more likely to happen in the cafe where heat 

 is applied partially ; for inftance, if a tea-kettle be placed at 

 the fide of the fire, fince the heat is then more flowly and 

 unequally diffufed through the body of the water. But after 

 the whole contents being fully penetrated, are warmed up 

 to the requinte degree of inccniity, the Ileam, as fall as it is 

 8 formed,. 



