B L A 



pktCi with equal propriety as to the foimer, regarding the 

 iinina:, packing, common builJiriE^, &c. 



Fij^. 4. is a plan and feilion of the fame furnace at F in 

 the cli-vatiun. 



The inner circles repreftnt the various diameters of the 

 interior of the cone, the letters in each correfpoiidiag. The 

 two external circles defcnbe the packing and lining ; and 

 the circle N exhibits the circumference of the common 

 building of the furnace, which, at this particular fedtion, is 

 26 feet ii. diameter. 



PlateWH. Jig. I. is the elevation of the interior of a fur- 

 nace of a plain conllruftion, and at one time very prevalent at 

 foundcries. This falliion was deemed to poflcfs its pecu- 

 liar merits, and Hill maintains its form unaltered at fome iron- 

 works where the regular tapering cone is not yet adjnittcd. 

 Its inferiority, as to height, is amply made up by an enlarged 

 capacity anfing from its diameter. 



Diameter at the mouth of the cone A - 3 feet 

 ditto - at - B - 1 1 



ditto at the bolhes - C - 1 2 



Height from C to B - - 12 feet 



from B to A - - 1 + 



Height of the bolhings and hearth not re- 



prcfented in the figure - - II 



Total height of that part of the fur- 



nace occupied by the materials - 37 feet 



FF, reprefents a view of the vertical method of carrying 

 off the moifture and fteam from the mafs of building, by 

 means of vents. The number of upright flues vary from tour 

 to eight, and have regular communications by means of hon- 

 zontal openings with the external air, GG. Thty are gene- 

 rally carried up parallel to the hning, and inchne with the 

 general diminution of the cone. The former, or vertical 

 openings, are fix inches fquare, and the horizontal commu- 

 nications four inches fquare. 



Fig. 2. is a plan and feftion oi Jig. i. in which are repre- 

 fented the lining, the vacuity for packing, and eight vents 

 or op'.'niiigs correfponding to thofe in the elevation. The 

 letters in each figure concfpond, and the two dotted circles 

 are meant to (hew, that occafionally all the vents communicate 

 with eacli other by means of a horizontal gutter, or channel, 

 carried quite round the building. This precaution ij ufcd lell 

 qny of the tubes were to fill up and choak the free circulation 

 of the vapour, that its appropriate quantity may get eafily 

 difchargtd amongft the other openings. 



Fig,^. is an elevated fection of a furnace, the interior 

 fhapc of which has now almoll become univerfal. The 

 Kegular and uniform defcent of the materials wliich follows, 

 as a confequence of the gradual enlargement of the cone, 

 fully jullifics the general partiality in favour of this fhape. 



Diameter at the mouth, or opening A - 3 feet 



Diameter at the top of the bofhcs B - 10 



Tlie height from B to A - - - 31 j- 



Height of the hearth and bofhes not feen in 



the plate - - - - ilj- 



Total height of this furnace - 43 feet 



This form of furnace is not only conllrufted with a 

 double lining of fire bricks CCCC, and two openings for in- 

 troducing fand for packing biii, but has alfo an opening 

 Dl), from top to bottom, about the centre of the common 

 building. From this, in all dircftions, proceed fniall vents^ 

 which communicate at a (hort dillancc with the open air, as 

 may be feen along the fides ot the building. 



J'ig. 4. is a plan and fecflion of Jg. 3. cut acrofs at B*. 

 8 



B L A 



B, diameter ovtr at the bofhes 10 feet. 

 CCCC, the two circles of fire brick hning, as feen in the 

 elevation. 



iiil), fpaces for receiving packing. 



DD, circular vent, or general gutter, from which ramify 

 the horizontal openings. 



Thcfe are repeated at intervals of four feet in the height, 

 as may be feen in the elevation. In building, DD is filled 

 with fragments of ioft fand-llone, which are eafily reduced 

 in the expanfion of the furnace, and tend, by diverting it* 

 real preflure, to preferve the body of the building entire. 



A fimilar want of unanimity of opinion fubfifts among 

 iron-makers, relative to the general conffruftion of the 

 bofiics, their particular height, and moil beneficial range. 

 Some contend for flat, others for hollies more vertical, whila 

 others again conceive the exertions of thofe equally fuccefsful, 

 who adopt the mean of the two extremes. At different 

 places, and to every polfible range, have been atributed the 

 moll important confequenccs in the fubfequent procefs. 



Plate IX. Jg. I . reprefents bofhes of the Heepcll conllruc- 

 tionl 



Diameter at A - - - 10 feet 



Perpendicular height from B to A - 8 



Square at . - ?• - - 2^ 



The opinion relative to this form is, that at firfl blowing, 

 the bolhes are produdtive of a very proper degree of fufpen- 

 fion of the materials ; but as the preffure of the defcent bears 

 in every direction upon the under or bottom part next the 

 fquare at B, it becomes increafed fo much, that the weight 

 of the incumbent materials early begin to prefs too much 

 towards the bottom of the hearth, counteraft the regular 

 precipitation which Ihould take place, and impede theafcent 

 and full effeft of the blall. 



Fig. 4, is a feclion of bolhes approaching to, or indeed 

 may be confidered as the oppofite extreme. Here the re- 

 verfe of the fadl attributable to N° i. takes place. The 

 preffure of the dcfcending material is equally diftributed 

 over the very flat inclination of the bofhes, and there is no 

 more weight deemed to be on ttie fquare at A than is equal 

 to a fidl column of the materials of fimilar dimenfions, left by 

 the diredt tendency which the llrength of the blafl to keep 

 them in a ftate of partial buoyancy. To counteract thefe 

 advantages in part, very ferious defects are here alfo imputed. 

 If circumllancts unite to increafe the tear and wear at A in 

 any uncommon ratio, either by fcouring, or from a defi- 

 ciency in tlie quality of the Hone or bricks, the whole of the 

 upper part of the hearth at B B is immediately expofed, and,, 

 though compofed of a fuperior quality of fand, will loon 

 follow the direction of the defcending current. A preffure 

 of materials then takes place, equal to the whole of the in- 

 creafed fpace, while the cffeft of the blafl to bear them up 

 is confiderably diminilhed by the enlargement of the original 

 diameter.. It will be feen from the plate tliat the weaknefs 

 of flat bofhes at the top is ill calculated to withfland any 

 accumulating preffure, and that by confining their part of 

 the procefs to the hearth, the latter mull loon, by a fimilar 

 widening^ be entirely dellroyed. 



Thole who wifli to lleer clear of extremes, or profit by 

 the more adventurous fpirit of their neighbours, more gene- 

 rally adopt a mode of bofhing that occupies the mean of the 

 two former extremes. This is reprcfented hyjg. 3,. 



Diameter of the bolhes at A - - - lo^ feet 



Perpendicular height from B to A - - 5 



Diameter of the fquara B. - - - 2j 



In general, the boflies of blafl furnaces are made of the 

 fame fand Hone with the hearths, but of late fire bricks have 

 been introduced, with a confiderable iudicatioi* of advautags. 



and 



