U R C 



U K E 



ufaal ftandard feems to have been between twelve and fix- 

 teen ounces. 



URCHIN, a common name given W) the hedge-liog. 

 Urchin, Sea, in Ichthyology. The echinus marinus of au- 

 thors is, in feme parts of England, called the Jea-egg, and 

 in others Xhe Jeo-urch'm, or hedge-hog. It is a genus of fi(h, 

 of which there are a great number of fpecies. See Echino- 

 DERMA, and Centronia. 



The manner of thefe creatures moving at the bottom of 

 the fea has been difputed among naturalifls ; the general 

 opinion of the world has been, that they did it by means of 

 their fpines or prickles, which ferved them by way of legs ; 

 but feme of late, particularly Mr. Gandolphe, pretend that 

 the fpines of the urchins are of no ufe to them on this occa- 

 fion, but that they move by means of certain legs, like the 

 legs of the ilar-fifh, which they occafionally put out when 

 they walk, and at other times retraft them into their body. 

 The world was readily falling into this fyftem, particularly 

 as Mr. Gandolphe affirmed, that he had been often an eye- 

 witnefs to it ; but the indefatigable M. Reaumur tried the 

 experiment himfelf, and often made himfelf an eye-witnefs 

 of the contrary faft, having frequently feen them walk at 

 the bottom of a (hallow bafon of fea-water, with no other 

 affiftance than that of their fpines, and even having made 

 them perform the fame motion, by the fame means, upon 

 his hand. 



This curious inquirer into nature did not, however, ftop 

 here ; but took occafion from hence to inquire accurately 

 into every circumftance of their progreflion, which is per- 

 formed by fo uncommon means. 



It is certain that the fea-urchin does throw out at the 

 lower aperture of the (hell, when it pleafes, certain bodies 

 which refenible not a little the legs of ftar-tl(h ; but thefe 

 ferve not at all to its motion ; but, on the contrary, their 

 real ufe is to keep the creature ftill, and fixed in the fame 

 pofition ; and, to defcribe them more exadly, they very 

 aptly reiemble the horns of fnails ; whence M. Reaumur 

 has chofen rather to call them horns than legs. The ufe the 

 urchin makes of thefe horns, while it is in motion, is to feel 

 about, and try the ground on which it marches ; and they 

 ferve the creature as a ftaff does a blind man in his walking, 

 to touch and try every thing that lies in the way ; and to 

 make them ferve to this purpofe, it is continually extending 

 or retrafting them during the time it is moving. Thefe 

 horns are not only placed about the orifice of the ihell, but 

 they are every where difperfed among the fpines, all over the 

 furface of the (hell. 



In order to underftand the pofition of thefe horns, we 

 muft confider, that the fea-urchin (hell is a hard body, ap- 

 proaching in form to that of a fegment of a fphere, with 

 two apertures, one commonly at the fummit of the (hell, 

 and another oppofite to it at the bafe : the former hole 

 ferves, as it is fuppofed, for difcharging the excrement, 

 and the latter for the mouth of the animal. The whole ex- 

 ternal furface is divided by protuberances, of different fizes, 

 into ten fpherical ifofceles triangles, which have their vertex 

 at the upper aperture, and their bale at the lower : five of 

 thefe are large and five fmall ; the larger are feparated from 

 the fmaller by triangular bands pierced with fmall holes, ar- 

 ranged in a beautiful and regular order. The triangular 

 fpaces are divided by feveral lines, commencing at the upper 

 aperture of the (hell, and terminating at the lower; thefe 

 lines are marked by fundry eminences of different fizes, each 

 of which refembles a fort of nipple : on thefe parts the bafe 

 of every fpme is fixed, and as the bafe is hollow, it is able 

 to turn round each eminence. Of thefe fpecies M. Reau- 



mur found more than two thoufand on every fifh ; and the 

 number of perforations on each fhell is not lefs than thirteen 

 hundred. From each of thefe perforations, there proceeds 

 a horn, which horns ai% only vifible when the fifh is in the 

 water, and even then it puts forth only fome of them at 

 once : thefe ferve as anchors to the fi(h, becaufe it glues 

 them fall to the (tones, &c. 



The fpines arc all capable of aflifting the creature in its 

 motions, but ihofe it principally employs are fuch as are 

 placed near its mouth ; as thefe can turn upon their balls 

 everyway with equal facihty, the creature finds it equally 

 eafy to move on any fide ; and when it has determined 

 which way it will move, thofe fpines which Hand direftly 

 toward that point, and thofe which are direftly oppofite, 

 are of equal fervice to it ; it draws itfelf forward by means 

 of the firft, and pufhes itfelf on with the others ; to do this, 

 it firft thrufts out the foremoft ones as far as pofiible, and 

 preffing them againft the bottom, it draws on its body by 

 them ; and this is fucceeded, by drawing up the hinder 

 ones clofe to its (hell, and then fixing them againft the bot- 

 tom, it pufhes itfelf forward by them. This is the manner 

 of this little creature's marching in the common way, with 

 its mouth downward ; but it has this ftrange fingularity, 

 that it is not confined to this pofture alone in marching, but 

 can, with equal eafe, walk with its mouth upwards, or run 

 along fideways in the manner of a wheel ; or in any direc- 

 tion between thefe. The legs and the horns cover all parts 

 of it, and are in every part of it equally able to move fepa- 

 lately thirteen hundred horns, and more than two thoufand 

 fpines, which ferve for legs. Mem. Acad. Par. 1712. 



URCI, in yincknt Geography, a town of Hifpania, in 

 Boetica, at the mouth of a river, on the frontiers of the 

 Tarragonenfis of Boetica. 



URCINIUM, a town fituatedon the coaft of the ifland 

 of Corfica, between Rhium Promontorium and Arenofuin 

 Littus. Ptolemy. 



URCIZE, St., in Geography, a town of France, in the 

 department of the Cantal ; 21 miles S. of St. Flour. 



URCOS, a town of Peru, in the diocefe of Cufco ; 20 

 miles S. of Cufco. 



URCUNAZO, a river of Spain, which runs into the 

 Orio, in the province of Guipufcoa. 



URDACHE, a town of Spam, in Navarre ; 22 miles 

 N. of Pamplona. 



URDASIM, a river of Ruffia, which runs into the 

 Ural, at Fort Tanalitzkaia. 



URDASIMSKAIA, a fort of RufTn, in the govern- 

 ment of Upha ; 128 miles E. of Orenburg. 



URDE', or Urdee, in Heraldry. A crofs urde feems 

 to be the fame with what we otherwife call ciechee. 



URDIALA, in Geography, a town of Spain, in the 

 province of Tavaftland ; 28 m.ilts W. of Tavafthus. 



URE, or YouRE, a river of England, in the county of 

 York, which rifes at and paffes by Ma(ham, Rippon, Bo- 

 roughbridge, &c. and about two miles below the laft town 

 joins the Swale, and takes the name of Oufe. 



Ure, in Rural Economy, a provincial term fometimes 

 applied to the udders of particular forts of domeftic animals, 

 as thofe of cows, (heep, and fome others. See Udder. 



UREA, or Ure'e. Fouicroy and Vauquelin gave this 

 name to a principle contained in human urine, which, in 

 combination with many others, Roiielle junior (irft pointed 

 out fo early as 1773 ; and the defcription of thefe cele- 

 brated chemifts, and that of Mr.Cruickfhanks, who examined 

 it about the fame time, have been generally adopted by fuc- 

 ceeding writers, with one or two exceptions only, even to 



the 



