ROL 



other branches of pure mathematics ; and fo great was his 

 fuccefs, that in 1685, three years only after his name was 

 firft known in the mathematical world, he was chofen a 

 member of the Academy of Sciences. In the year 1690, 

 M. Rolle publifhed a treatife on Algebra, which was fol- 

 lowed by a new work, entitled " A Demonftration of a 

 Method for the Refolution of Equations of all degrees ;" to 

 which fucceeded two other methods ; by the firft of which 

 the fame equations are refolved geometrically ; and by the 

 fecond, feveral unrefolved queftions of Diophantus are an- 

 fwered. In the year 1699 he publifhed a work, entitled 

 " A Method of refolving indeterminate Queftions in Alge- 

 bra," and he was appointed fecond geometrical-penfionary 

 of the Academy of Sciences. About this time he united 

 with that party in the Academy which oppofed the new geo- 

 metry, and carried on a controverfy ag.tinlt the marquis de 

 l'H6pital, on the fubject of infinitefimals, till the fociety 

 impofed filence on all the difputants. M. Rolle thought 

 that his favourite fcience, algebra, was capable of almoft 

 indefinite improvement, and he announced his defign of 

 drawing up entirely new elements, but death put an end to 

 his plans. He died in 1719, in the 68th year of his age, 

 having uniformly borne an excellent character for piety, 

 probity, and amiable manners. Befides the works already 

 mentioned, many curious papers were communicated by him 

 to the Academy of Sciences, and may be found in their 

 " Memoirs," from the year in which he took his feat in that 

 body till 1 7 14. The higher branches of the mathematics 

 are the fubjects of almoft all tliefe papers. 



Rolle, Johann Heinrich, the youngeft of three bro- 

 thers, all eminent muficians, and fons of a father who, as 

 mufic director at Magdeburg, had rendered the name illuf- 

 trious. Henry, who fucceeded his father as mufic-director 

 in his native city, was born in 17 18, and died in 1785. He 

 was an excellent compofer for the church, as well as author 

 of pieces for the organ and harpfichord of great merit. His 

 oratorio of " Thirfa and her Sons," is full of good tafte, 

 new pallages, pleafing effects, and true pathos. 



Rolle, Fr. a part in Mufic and Dramatic Works. The 

 French have a diftinct term in mufic for a vocal and inltru- 

 mentsl part in an opera or concert. The finger's or the 

 actor's part in an opera or play, is equally termed rolle; 

 in a concert or opera each inftrumental part is called partle. 

 We make no diftindtion, in England, between a vocal or 

 inftrumental part in an opera or concert ; each is called 

 part : as the part of Hamlet, in a play, of Mandane, in 

 an opera ; the firft violin, tenor, or violoncello part needs 

 no other diftindtion than the name of the character, or 

 inftrument. 



Rolle, in Geography, a town of Switzerland, and ca- 

 pital of a lordfhip, lituated on the N.W. fide of the lake 

 of Geneva ; 14 miles S.W. of Laufanne. 



ROLLER. See Roll. 



Roller, in Gunnery, a round piece of wood of about 

 nine inches diameter, and four feet long, which ferves in 

 moving mortars from one place to another, when near. 

 This is done by railing the fore-part of the bed fo high that 

 a roller may be laid under it ; then pufhrng the bed for- 

 wards, and laying another in its way, and another before 

 that, and fo on, the mortar is eafily moved. 



RoiXEB is alfo a fmall wheel placed at the foot of the 

 hammer of a gun, or piilol-lock, in order to lelTen the fric- 

 tion of it againft the hammer or feather-fpririj 



Roller, in Agriculture, a well-known implement formed 

 of wood, caft-iron, or ftone, fo as to turn upon its axis, 

 and be drawn over the furface of the land by means of 

 horfes, for the purpofe of reducing the lumpy or cloddy 



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ftate of tillage lands, and rendering thefe, as well as thofe 

 of the grafs kind, fmooth and even. They are conftru&ed 

 in different ways for different purpofes, and of different fizes 

 and weights to fuit different ufes in hufbandry. They are, 

 however, in general diftinguifhed into the tillage and grafs 

 kind. It has been a matter of difpute, whether rollers with 

 large or fmall diameters have the advantage, in point of effect 

 upon the land. It is probable that there may be incon- 

 venienciesin both extremes. The roller fhould not, however, 

 be fo fmall as to require much loading, as by fuch means 

 much time and labour are loft. A late practical writer, 

 however, advifi-s that in conftructing heavy rollers, the 

 workmen fhould be careful that they have not too great a 

 diameter, whatever the material be of which they are 

 formed, as the preffure is diminifhed where the implement is 

 of very large fize, by its retting on too much furface at 

 once, except an addition of weight in proportion be made. 

 By having the roller made fmall, when loaded to the fame 

 weight, a much greater effect; will be produced, and a con- 

 fiderable faving of expence be made in the conllruction of 

 the implement. And he recommends that all the larger 

 forts of rollers fhould have double fliafts, in order that they 

 may be drawn by two horfes abreaft ; and fuch as are em- 

 ployed for arable lands fhould have a fcraper attached to 

 them. This addition, he thinks, faves much time, and pre- 

 vents the driver the trouble of conftantly fcraping the ma- 

 chine, efpecially in wet feafons, and clayey tenacious lands. 

 Strong frames are alfo neceffary for rollers, fo that proper 

 weights may be put upon them ; and open boxes or carts 

 placed upon them may fometimes be requifite, in order to 

 contain any additional weight that may be thought proper, 

 as well as to receive ftones or other matters that may be 

 picked up from the ground. Pieces of wood or ftone, as 

 heavy as a man can lift, are the molt fuitable fubftances for 

 loading thefe implements with, where they have not the advan- 

 tage of boxes for the purpofe of containing fuch weighty 

 fubftances. 



There has been much inconvenience experienced in the 

 ufe of this fort of implement in turning at the ends of 

 ridges, fields, or other places, from their not moving upon 

 their axes, but being drawn along the furface of the ground, 

 by which they are liable to tear it up, and make deep hole6 

 and deprefiions before they come again into the direct line 

 of draught, and are not brought round without great exer- 

 tion in the teams : it has therefore been attempted, in order 

 to obviate thefe inconveniencies, to conftruct rollers in two 

 pieces, and by the divifion in the middle to enable the dif- 

 ferent parts to twift round on their proper axes, one forward 

 and the other in a retrograde direction. When formed in 

 this way, the cylinders are bell made of caft-iron, as they 

 turn with greater eafe and readinefs. 



Roller, Common. This is a fort of roller which is em- 

 ployed for the common purpofes of tillage, and which is 

 moltly ufed for rolling wheat in the fpring, and grafs-feeds; 

 they are generally about five or fix feet long, and from fif- 

 tnii to thirty inches in diameter ; but thofe employed for 

 flattening one-bout ridges, in order to prepare them for 

 drilling turnips upon, are commonly (liorter and of much 

 lefs diameter, and frequently attached to the drilling im- 

 plement. 



But of the various kinds of thefe rollers that are made 

 ufe of, Mr. Morley of Newark thinks that thofe of the 

 belt conftruction, and which anfwer the molt perfectly in 

 practice, are Inch as are made of caft-iron, and divided into 

 two parts: the length from time hot to three feet fix 

 indies, covering a furface of from fix to leven feet, and 

 being above ten hundred weight s the frame fhould be made 



