CONCHOLOGY. 



n? 



if this does not fucceed, feal-fkin, or fifh-flcin, and pu- 

 mice-ftoiie, are to be employed. When a fiiell has a thick 

 cru!t, which will not give way to any of thefe means, the 

 only mode left is to plunge ir ieveial times into itrong 

 aquafortis, till the ftubborn cruft is wholly eroded. The 

 limpets, aurts marine, helmet-flielh, and feveral oiher 

 fpecies of this kind, nuift have this fort of management ; 

 but as (he delign is to (how the hidden beauties under 

 the criift, andnot to deftroy the natural beauty and po- 

 lifli of the infide of th'fe (liell, the aquafortis fliould be ufed 

 in the following manner : A long piece of wax mud be 

 provided, and one end of it made perfectly to cover the 

 whole mouth of the fliell ; the other end ferves as a han- 

 dle, and the mouth being Hopped by the wax, the liquor 

 cannot get in to the infide to fpoil it ; then there muft be 

 placed on a table a vtli'el full of aquafortis, and another 

 full of common water. The fliell is (o be plunged into 

 the aquafortis, and after ren\aiuiiig a few minutes in it, 

 is to bd taken out, and plunged into the common watei'. 

 The progrefs the aquafortis makes in eroding the fiirface 

 is thus to be carefully obferved every time it is taken 

 out : the point of the (liell, and any other tender parts, 

 are to be covered with wax, to prevent the aquafortis 

 from eating them away; and if there be any worm-holes, 

 they alio mult be flopped up with wax,otherwife the aqua- 

 fortis will quickly eat through in thofe places. When 

 the repeated dippings into the aquafortis fiiow that the 

 coat is fufiiciently eaten away, then the (hell is to be 

 wrought carefully with fine emery and a brufli ; and when 

 it is poliflied as high as it will bear, it muft be wiped 

 clean, and rubbed over with gum-water, or the white of 

 an egg. In this fort of work the operator (hould wear 

 gloves, otherwife the lealt touch of the aquafortis will 

 burn the fingers, and often, if not regarded, eat away 

 the fkin and the nails. 



Thefe are the methods to be taken with fliells which 

 require only a moderate quantity of the furface to be 

 eaten off; but there are others which require to have a 

 larger quantity taken off, and to be uncovered deeper : 

 this is called entirely fcaling a (liell. This is done by means 

 of a horizontal wheel of lead or tin, im.pregnated with 

 rough emery; and the (liell is worked down in the fame 

 aiianner in which (tones are wrought by the lapidary: 

 both figures of the nautilus-(hell given in the Ccnchology- 

 Plate III. were worked down in this manner. Nothing 

 is more difficult, however, than the performing this viork 

 with nicety ; very often (hells are cut down too far by it, 

 and wholly fpoikd : and to avoid this, a coarfe vein muft 

 be often lett ttanding in fome place, and taken down af- 

 terwards with th'e file, when the cutting it down at the 

 wheel woidd have defaced the adjacent parts. 



After the fliell is thus cut down to a proper degree, it 

 is to be polifiied with fine emery, tripoli, or rotten (tone, 

 with a wooden wheel turned by the fame machine as the 

 leaden one, or by the common method of working with 

 the hand with the l.ime ingredients. When a fliell is full 

 of tubercles, or protuberances, which are to be prefervtd, 

 it is then impoflible to uie the wheel ; and if the common 

 way of dipping into aquafortis be attempted, the tuber- 

 cles being harder than the reft of the (hell, will be eaten 

 through before the reft is fufficiently (caled, and the (hell 

 will be Ipoiled. In this cafe, indultry and patience are 

 the only means of effecting a polifti. A camel's-hair pen- 

 cil mult be dipped in aquafortis, and with this the inter- 

 mediate parts of the (hell muft be wetted, leaving the pro- 

 luberances dry ; this is to be often repeated, and altera 

 few moments the fliell is ;dways to be plunged into wa- 

 ter, to ftop the too great erofion of the acid, which would 

 otherwile penetrate too deep, and deftroy the beauty of 

 the fliell. When this has fufiiciently taken o(F the foul- 

 , nefs of the fliell, it is to be polilhed with emery of the 

 fineft kind, or with tripoli, by means of a fmall ftick, or 

 the common polifhing-lloiie uled by the goldfmiths. This 

 is a very tedious and troublefome operation, efpecially 

 when the echinated oyfters and raurices, and other limihu- 

 Vol. V. No. 152. 



(hells are to be wrought; and what is worft of all, is, tha' 

 when this labour has been employed, the bufinefs is not 

 fufiiciently done; for there ftill remain feverai places which 

 could not be reached by any inftrument, fo that the (IkU 

 muft be rubbed over with gum-water or the white of sn 

 egg, in order to bring out the colours, and give a glof; ; 

 in fome cafes it is even necefi'avy to add a coat of varnifli. 



Thefe are the means ufed by artifts to brighten the co- 

 lours and add to the beauty of (hells ; and the changes 

 produced by poliftiing in this manner are ib great, that 

 the fiiell can fcarcely be known afterwards to be the iame; 

 and lience we fometimes hear of new (licHs in the cabinets 

 of colleitors, which have no real exiftence as feparate 

 fpecies, but are (hells difguifed by polifhing, and are thus 

 fraudulently impofed upon the hafty and unwary collec- 

 tor. To caution the young conchologlft againft errors 

 of this kind, it may be proper to mention the moft re- 

 markable fpecies thus ufually altered. The onyx-(heil or 

 volute, called the purfi'e or 'viokt-tip, which in its natural 

 ftate is of a fimple pale brown, when it is wrought flightly, 

 or polifiied with only the fuperhcies taken off, is of a fine 

 bright yellow ; but when it is eaten away deeper, it ap- 

 pears of a fine milk white, with the lower part bluifli : it 

 is in this ftate called the oiiyxjlell ; and it is preferved in 

 many cabinets in its rough ftate, and in its yellow appear- 

 ance, as different Ipecies of (hells. 



The violet (hells, lb common among the curious, is s. 

 fpecies of porcelain, or common cowry, which does not 

 appear in that elegance till it has been polifiied ; and the 

 common auris marina (hows itfelf in two or three diffe- 

 rent forms, as it is more or lefs deeply wrought. In its 

 rough ftate it is dulky and coarfe, of a pale brown on the 

 outfide, and pearly within ; when it is eaten down a little 

 way below the furface, it (hows variations of black and 

 green ; and when ftill farther eroded, it appears of a fine 

 pearly hue within and without. The nautilus, when it is 

 poiiftied down, appears all over of a fine pearly colour; 

 but when it is eatenaway but to a fmall depth, it appears 

 of a fine yellow i(li colour with dulky hairs. The buigau, 

 when entirely cleared of its coat, is of the moft beautiful 

 pearl-colour ; but when flightly eroded, it appears of a 

 variegated mixture of green and red, whence it has been 

 called the parroquet. The common helmet-lhell, when 

 wrought, is of the colour of the fineft agate; and the 

 raufcles, in general, though very plain (hells in their com- 

 mon appearance, become beautiful .when polifiied, and 

 (how large veins of the moft elegant colours. The Perfiaii 

 fliell, in its natural Itate, is all over white, and covered 

 with tubercles; but when it has been ground down on a 

 wheel, and polifiied, it appears of a grey colour, with 

 fpots and veins of a bright and highly polifiied white. 

 The limpets, in general, become very different when po- 

 lifiied, moft of them (hewmg bright and elegant colours; 

 among thefe the tortoile-fiiell limpet is the principal ; it 

 does not appear at all of that colour or tranfpaience till it 

 has been wrought. , 



That elegant fpecies of (hell called the jcnquil-chnnia, 

 which has deceived (o many into an opinion of its being 

 a new fpecies, is only a white chami with a reticulated 

 furface ; but when this is polilhed, it loles at once its reti- 

 cular work and its colour, and becomes perfcflly fmooih, 

 and of a fine bright yellow. The violet-coloured chama 

 of New England, when worked down and polifiied, is of 

 a fine milk white, with a great number of blue veins, dif- 

 pofed like the variegations in agates. The afi'es-ear (hell, 

 when p'.'ilhed after working it down with the file, be- 

 comes extremely glofi)', and obtains a fine rofe-colour all 

 about the rnouch. ^ Thefe are fume of the moft frequent 

 among an endlefs variety of changes wrought on (hells 

 bypoli(hing; and we find there are n>any of the very 

 greatelt beauties of this part of the creation which mult 

 have been loft but for this method of fearching deep into 

 the fubltance of the fliell for them. 



The Dutch aie very fend of fliells, and are very nice 



in thtjr manner of working them : they are under no rc- 



L Itraint, 



