Page:The New International Encyclopædia 1st ed. v. 17.djvu/253

ROLLER. 229 ROLLING MILL. common roller (Coracius yarnila), a bird nearly eiiual in size to a jay. Besides the genus Cora- oias, there are the broad-billed rollers of the genus Eurystonius, found in Africa and trojjieal Asia, and at least four genera of remarkable rollers confined to Madagascar. ROLLERS. See Eoad axd Street lUcnix- ERY. ROLLER WORM, or ROLLWORM. The larva of a liesperid butterlly [Eudainus i)i()teus), which rolls the leaves of beans and peas in the Southern Atlantic States. The large eggs are laid upon the leaves in clusters of from four to six. The larva, which is yellow-green and has a slender neck and large head, cuts a slit in the leaf from the edge, rolls the llap around its body, and works from the inside of this roll with its soft parts perfectly protected. When fully grown it is 1..5 inches long, and transforms to a chrysa- lis within the leaf-roll. The adult butterfly is dark brown, the front wings having several sil- very white spots. In a small garden it may be kept in check by hand-picking, but the use of an arsenical spray is necessary in large fields. ROL'LETT, HEEM.iXX (1819-1004). An Ans- Iviaii jiiji't and art critic, born in Baden, near Vienna. Because of the radical tone of his po- litical poetry, Friihlingsboteii aus Oesterreich (1S4.5). published while he was in Germany, he was forbidden to return to Austria, and was later expelled from several German States. His princi- ytil works are : Frische Lieder I 1848, 2d ed. 1855 ) ; Ii'c publika iiisches Liederbuch ( 1848) ; Die Kinncs. a .series of songs, with music by Abt (1854); Offcnbaningen (2d ed. 1870) ; and Miirchen- gcschichtCH aus dem Leben (1894) . Rollett wrote some dramas and also two valuable works on art. Die drci MeiKter der Gemmogli/plik (1874), and Die Goethe-Bildmsse (1882). ROLLIN, ro'laN', Cii.4.eles (1661-1741). A French historian, born in Paris. He studied at the ColI6ge du Plessis, where, in 1683. he became assistant to the professor of rhetoric, and five years later he was made professor of eloquence in the Coll&ge de France. In 1694 he was chosen rector of the University of Paris, a dig- nity which he held for two years, distinguishing himself by many useful reforms. In 1696 he was appointed coadjutor to the principal of the Col- lege de Beanvais; but being an ardent Jansenist. he was removed in 1712, through the influence of his opponents. In 1715 he published an edition of Quintilian, and in 1726 the Traite des etudes, his best literary performances. After a long life of retirement devoted to writing and study. Eollin died in Paris, September 14. 1741. ' His most famous work is the compilation, for- merly of great popularity, known as the nistoire oieienne (13 vols.. Paris, 1830-38). which has frequently been reprinted and reedited both in French and in English, but is of little historical value. He also began a Uisloire romninc. which was completed by Crevier and other historians after Rollin's death, and was published in 9 volumes (Paris, 1738-48). ROLLIN, Ledru-. See Ledru-Rollin. ROLLING MILL. An establishment provid- ed with macliinery for working metal ingots into rails, bars, plates, rods, and structural shapes by repeatedly passing them when intensely hot be- tween cylindrical rolls. The three principal methods of working nielals are founding, forging, ami rolling, and of these three melhodt that of rolling has been ehielly instrumental in e.tvnding the use of metal for structural purposes to ita present enormous ilimonsions. The rolling niill was invented l)y Henry Corl, an KnglUluiian, in 1783, and although womlerfully developed in its essential principle, the device has undergone but little change since its invention. Rolling mills may be classified as two-high mills, three-high mills, ami four- high mills, with their modifica- ^::^^< — «t tions. The accompanying dia- grams show the |)rineiple of ojier- ation of each of these mills. Fig. 1 indicates a tuo-high mill in which the metal passes between the two rolls in the direction indicated [>y the lower arrow and has work done on it and then is returned over the rolls as indicated by the upper arrow for the second jiass. In the three- high mill, indicated hy Fig. 2, the metal passes forward be- tween the bottom and middle rolls and is returned Iwtween >** — ^ — ^ the middle and top rolls and has work done on it in both the forward and retuin passes. The four-high mill, as shown by Fig. "**< 3, consists essentially of two two-high mills placed one above the other nearly, an<l working in opposite directions so that p,(. ., the metal is acted upon during lioth the forward ami return passes. In actual practice the four-high mill ia seldom used. The original mill invented by Cort was a two-high mill 0])erating as indicated by Fig. 1. As will be seen, the metal after each forward pass had to be re- turned over the top of the mill, without any work being done on it, to get it into posi- tion for the next forward »♦- pass. Tliis operation, it will be readily understood, necessi- tated a material loss of time and heat while the metal was being returned for each sue- — :* — *** ceeding pass through the rolls. Tile first great improvement of the two-high mill was de- signed to avoid these losses and consisted in ojierating the rolls by a reversing engine, which, as soon as the metal had completed the forward pass, reversed the direction of the rotation of the rolls and permitted the metal to be returned be- tween them. The chief disadvantages of revers- ing were that more expensive engines were re- quired, the whole machinery had to be heavier and more costly in construction, and the ex- pense of repairs was greater. The three-high mill, as will be seen from Fig. 2. has the great advantage over the two-high mill that the ndU operate all the time in one direction. On the other hand, the metal has to be lifted for each return pass. In modern rolling-mill practice, the lifting is done by hand when light material such as rods, bars, hoops, etc.. is being rolled and bv machinery when the material is hea. Fio. 3.