302 



COHORT COINAGE. 



faces. The last figure is then secondary. Its forma- 

 tion lias generally been quoted to illustrate the law 

 of decrement, as it has been termed, and it is easy to 

 represent it, although coarsely, by models. " But 

 If," says M. Hauy, " for this kind of rude masonry, 

 which, however, has the advantage of speaking to 

 the eyes, we substitute the infinitely delicate archi- 

 tecture of nature, it will lie necessary to conceive 

 i lie nucleus as consisting of an incomparably greater 

 number of imperceptible molecula?, and then tin- 

 number of lamina} of suprepositiou being itself con- 

 siderably augmented, while their thickness has be- 

 come imperceptible, the channel which these lamina; 

 form at their edges will likewise escape our senses." 

 Hence the surfaces of crystals appear to us planes. 



The facts which have been discovered, relative to 

 the laws of decrement, are sufficient to prove that an 

 immense variety of crystals may be made to grow 

 out of the combinations of the particles producing 

 the primitive forms, for the decrements may take 

 place on the edges, or parallel with the faces of the 

 primitive forms, on the angles, in which the lines are 

 parallel with the diagonals of the faces, in lines pa- 

 rallel to those which intersect the diagonals and faces, 

 constituting the intermediate decrements, or in a 

 mode which combines, more or less, the decrements 

 already mentioned, and which is, therefore, said to be 

 mixed. These primary decrements may be so modified, 

 as that they shall take place on certain edges or cer- 

 tain angles only ; or in uniform and alternate ranges ; 

 or from one edge, or one angle to another ; or, at the 

 same time, on all the edges and all the angles, &c. 

 Nevertheless, such is the fecundity allied to this sim- 

 plicity, that, when limited to ordinary decrements, 

 and to form ranges on the edges and the angles of a 

 rhomboid, it may be demonstrated, that this species 

 of nucleus is susceptible of producing 8,388,640 va- 

 rieties of distinct forms. 



COHORT. See Legion. 



COIMBETORE, or COIM BETOOR ; a province 

 of Hindostan, in Mysore, and southern part of the 

 dominions of Tippoo Sultan. The country is sepa- 

 rated from the country of Travancbre, Cochin, and the 

 Nayrs, by lofty mountains called the Western 

 Ghauts ; a continuation ot which also bounds it on 

 the north. On the east it is bounded by the Carnatic, 

 and south by Dindigul ; and it is divided into north 

 and South Coimbetore. It is fertile, producing su- 

 gar, cotton, rice, and l)etel leaf; and well watered 

 by several rivers. The principal towns are Coimbe- 

 tore, Erroad and Carroor. In 1799, on the death of 

 Tippoo, and the division of his territories, Coimbetore 

 was ceded to the East India company. 



Coimbetore ; a town of Hindostan, and capital of 

 the province to which it gives name ; situated at the 

 foot of the Western Ghauts, on the river Noyel ; 

 ninety miles S. Seringapatam, 252 S. W. Madras ; 

 Ion. 77 7' E. ; lat. 10 58' N. ; population, 12,000 ; 

 houses, 2,000. This city formerly contained upwards 

 of 40,000 inhabitants ; but it suffered much by the 

 wars of the British and the Mysore sovereigns. It 

 is now recovering. The exports are tobacco, cot 

 ton, thread, cloth, sugar, betel, &c. 



COIMBRA (anciently Coimbriga Coimbrica) ; a 

 city of Portugal, capital of the province of Beira, situ- 

 ated on a mountain, near the river Mondego, ninety 

 miles N. N. E. Lisbon ; Ion. 8 25f W. ; lat. 40 

 13' N. : the population was lately given at 15,200 ; 

 but the disturbances in Portugal have, according to 

 recent accounts, reduced the number much. It is a 

 bishop's see, and seat of the inquisition. It contains 

 a cathedral, seven churches, an hospital and a uni- 

 versity. It was built by the Romans, about 300 

 B. C. The university was originally founded in 

 A. 1>. 1291, at Lisbon, but was transfe A hither 



in A. D. 1308, and is now the only one in Portugal. 

 It consists of eighteen colleges with ample funds. 

 The course of study here is divided into six brandies, 

 viz. theology, taught by eight professors : canon law, 

 by nine ; civiL law, by eight ; medicine, by six ; ma- 

 thematics, by four ; and philosophy, by four. The 

 number of students in 1804, was 1431, and in 1817, 

 about 1400. To the university belong a botanic 

 garden and a library of 40,000 volumes. The aque- 

 duct on twenty arches, is remarkable. The envi- 

 rons of Coimbra produce oil, wine, and lemons. The 

 inhabitants manufacture linen, pottery, earthenware , 

 articles of horn, and wooden toothpicks. 



COINAGE, is the art of converting pieces of me- 

 tal into current coins, for the purposes of commerce. 

 The metals to be coined, having been first melted, 

 are reduced into plates of the requisite thickness, by 

 being passed repeatedly between the steel cylinders 

 of laminating and drawing machines. These thin 

 plates are then subjected to the action of a cutting 

 jut press, by means of which they are divided into 

 circular pieces, nearly of the size of the intended coin, 

 in which state they are called blanks. These are 

 then carried to the sizeing room, where each indivi- 

 dual piece is adjusted to "its standard weight. The 

 pieces which are too light, are selected to be again 

 melted ; and those which are too heavy, are subject- 

 ed to the action of a rasp or file. The pieces thus 

 adjusted, being in a state of great hardness, from 

 compression by the rolling and drawing processes, 

 by which all their latent heat had been squeezed out, 

 are again subjected to the action of a clear red heat 

 in a reverberatory furnace, after which they are boil- 

 ed in very weak sulphuric acid, which makes them 

 perfectly clean. After having been dried either in 

 warm saw dust, or over a very slow fire, they are in 

 a state for the two succeeding processes of milling 

 and stamping. The operation of milling is perform- 

 ed round the edge to prevent their being clipped or 

 filed. The principal pieces of this machine, are two 

 thin steel plates, about a line or the eighth of an inch 

 thick, one-half of the milling or legend, or of the 

 ring, is engraved on the thickness of one of these 

 lamina, and the other half on the other, and these 

 two plates are straight, although the blank or coin 

 to be marked by them is circular. The blanks (or 

 planehets as they are also called) are put in be- 

 tween these lamina in such a manner, as that each 

 of them being laid flat upon a copper plate, which is 

 fastened upon a very thick wooden table, and the 

 planchet being likewise laid flat upon the same plate, 

 the edge of the planchet may touch the two lamina 

 on each side, and in their thick part. One of these 

 lamina being immovable, and fastened by means of 

 several screws, the other is made to slide by means 

 of an indented wheel, which is made to receive the 

 teeth that are upon the surface of the steel lamina. 

 This sliding plate makes the circular piece of metal 

 turn round hi such a manner, that it remains stamped 

 on the edge, when it has made one turn. Only 

 crown, and half-crown pieces can bear the impression 

 of letters on the thickness of their edges. 



The coining engine, or mill, is so constructed, that 

 one workman may stamp 20,000 coins in a single 

 day. Gold, silver, and copper planehets, are all of 

 them coined in a mill, into which the coining squares, 

 or dies as they are called, are fastened. That of the 

 face underneath in a square box, garnished with male 

 and female screws, to fix and keep it steady ; and the 

 other above, in a little box furnished with similar 

 screws to fasten the coining square. The planchet 

 is laid flat on the square of the effigy, which is dor- 

 mant, and the bar of the mill being immediately 

 pulled by its cords, causes the screws set within it to 

 turn. This enters into the female screw, which is in 



