R O L 



iron which is fubjeded to this procefs is brought to the 

 mill Plate IV. before defcribed, from the forge hamn . 

 in bars of a fize proportionate to the nail rod it is intended 

 to make : thefe are cut into lengths by the (hears, and heated 

 in the furnace, then rolled repeatedly through the rollers, 

 C D which are reduced every time it panes, until the bar 

 becomes of the thicknefs for the fquare of the intended rod, 

 half an inch for inftance, and two, or two and a halt, inches 

 wide : it is, in this date, prefented to the btnE, F, and 

 one end being introduced between the guide-bars of the 

 flitters, is drawn in between them by the motion, and, by 

 this means the ring of one roller preffes a correfpondmg 

 breadth of the hot metal into the fpace between the rings or 

 the other roller ; this being performed by both rollers, com- 

 pletely divides the bar into feveral rods of the fame breadth 

 with the rings of the rollers. A fmall leaden p.pe is fixed 

 over the cutters, and being perforated with holes, conftantly 

 lets fall a fupply of cold water on the rollers, to prevent their 

 becoming hot, and thus lofing their hardnefs, which alone 

 nreierves their circular figure under the mtenfe preflure they 

 have to fufttun in dividing the iron. The guide-bars are 

 intended to force the iron rods, when cut out of the 

 grooves between the rings of the collar which they would 

 nototherwife quit, alter being fc> forcibly prefled into hem 

 by the rings of the oppofite roller. For making fmall 

 hoops, the rods, as foon as they are formed, are put through 

 the plain rolls again, and flattened into a hoop. 

 ' Rollini of Iron Hoops.-U the country thefe are made from 

 iron bars, which are reduced in rollers, iimilar to jig. 4, to a 

 fize proper to produce the hoops required ; thefe are cut into 

 Wins, heated, and palled through the Hitters, which d.v . : 

 the! into three or four rods, winch are immediately pre- 

 fentedto the cafe-hardened rolls, and flattened out into a 

 proper hoop. The mill (hewn in Plate IV. is equally 

 adaoted for this work as for nail-rod ; but for hoops, the ad- 

 dition of a proper fly-wheel would be an improvement, as 

 the work is fo much heavier. . 



In London, where a vail quantity of old hoops is to be 

 procured, they are re-manufactured, and make the very belt 

 fort The victualling-board alone coniume many hundred 

 tons' annually for the fervice of the navy : the old hoops 

 are made up into faggots, and mingled, or welded into bloom 

 at one heatfby a forge-hammer, or in imall works by rollers 

 like Plate V fit- «■ The blooms ' bel "g a S am heated > arc 

 rolled out into bars by the bar rollers,^. 4, and thefe are 

 cut into two or three lengths, according to the fee. of the 

 intended hoops ; thefe pieces are heated a third tune, flu 

 into rods as above defcribed, and then formed into hoops by 

 the cafe-hardened rolls. By fucceffive improvements it has 

 been found, that two heats are fumc.ent, the hr for min- 

 gling and forming the bars, and the fecond for flitting .and 

 flattening the hoops ; but in either method the grand objeft 

 , roting and rolling, always in the direftion of the 

 length, to gain a fibrous texture to the iron. 



Old hoops have been lately made up into new atone 

 ration ; by employing a greater power and veloci. 

 makinn- up a fmaller quantity at once, it may be effefted at 

 , fmele heat, inftead of two or three. For this purpoC 

 old hoops are cut into flvort lengths and faggoted in pdes, 

 the rivets being firltcutont and the pieces ftraightened, that 

 tie piles maybe more clofe and compaft : thefe piles are 



heated in the ulual kind of furnace to a good welding he I d 



arc rolled between the (hingling rollers, being paffed through 



two or three grooves till they arc properly reduced to go 



through the flat-grooved bar roller,: after rolling thi 

 the three grooves thereof, they are put through the Hat pj ,, . 

 and a guide is ufed to direct them ftnngtlt forwards, Without 

 Vol. XXX. 



ROL 



care or attention from the workman. The bar is then car- 

 ried to the cutters, and flit into two or more rods, which are 

 immediately and fucceflively patted between a pair of plain, 

 cafc-hardened rolls, to iinifh the hoops. 



Vat-hoops, or others above two inches in width, do not 

 require to be flit, but are at once carried from the bar rollers 

 to the plain rollers, which finilh them. The piles for fhin- 

 gling mult not be made too large, or the hoops will not retain 

 fufficient heat to be found ; about 42lbs. will be a proper 

 quantity. The mill for this manufacture muft of courfe 

 have great power, and the rollers fliould move with a fuffi- 

 cient velocity to enable the iron to be got through the whole 

 procefs whilll fufliciently hot. The bar and fhingling 

 rollers Ihould be placed clofe together in a line, and muft 

 make about 90 revolutions per minute ; the cafe-hardened 

 rollers (hould make 140 per minute, and fliould be placed in 

 fuch relative fituations as will be moll convenient to convey 

 the iron in the quickeft manner from one pair to the next- 

 A patent has been taken out by fomc, who pretend to the 

 invention of the above method ; but they cannot prevent 

 other manufacturers ufing it, as it is no new invention, con- 

 futing only in taking more care, and ufing rollers with a 

 greater velocity. 



The rolling-mill is not confined to the laminating of iron, 

 but is likewife employed very extenfively for reducing brafs, 

 copper, tin, lead, as well as gold and filver, into plates and 

 bars. The latter metals are fcarcely ever reduced by any 

 other means than rolling ; as this method makes no walle, is 

 the moll expeditious, and produces better work than ham- 

 mering, or any other method, particularly when an equality 

 of thicknefs and an even furface are defired ; fuch, tor ex- 

 ample, as gold or filver, which is always to receive a polifh ; 

 in thefe cafes the rollers are made of Iteel hardened and po- 

 liflied on the furface with the molt fcrupulous nicety, that 

 they may produce a perfect furface on the matters which 

 have been palled through them. 



RoLL\KV-Prefs Printing. See PRINTING. 

 Rolling, in Sea Language, that motion by which a (hip 

 vibrates from fide to fide. Rolling is, therefore, a fort of 

 revolution about an imaginary axis, pafling through the 

 aentre of gravity of the (hip ; fo that the nearer the centre 

 of gravity is to the keel, the more violent will be the roll ; 

 becaufe the centre about which the vibrations are made is 

 placed fo low in the bottom, that the rcfiltance made by the 

 keel to the volume of water which it difplaces in rolling, bears 

 very little proportion to the force of the vibration ah ivi 

 the centre of gravity, the radius of which extends as high as 

 the mail-heads. But if the centre of gravity is placed higher 

 above the keel, the radius of the vibration will not only be 

 diminifhed, but fuch an additional force to oppofe the motion 

 of rolling will be communicated to that part of the iliip's 

 bottom as may contribute to dimkiifh this movement con- 

 (iderably. 



It may be obferved, that, witli refpeft to the formation 

 of a (hip's body, that (hape which approaches nearefl to a 

 circle is the molt liable to roll ; .is it 1, evident, 1l1.1t if this 

 be agitated in the water, it will have nothing to reitrain it ; 

 becaufe the rolling or rotation about it- centre dilplaccs no 

 more water than when it remains upright ; and hem 

 becomes neceflar) to ujcreafethe depth of the hold, the ri 

 of the floors, ami dead or rifing-wood ifore and abaft. See 



SlIIP-BI ilium;. 



R.OLLING-7iWAf. See TACKLE. 



Rolling Fori, in Geograpfjy', ■ ol Kentucky, 



which run- into the Ohio, N. hit. 5; 47'. W. lo | 

 86 18'. 



ROLLO, in Biography, the tirltdukeof Normandy, was 

 t, L originall) 



