SHELLS. 



wife the aqua forti'3 would foon eat through in thofc places. 

 ' When the repeated dippings into the aqua fortis fliew that 

 the coat is fufficiently eaten away, then the fhell is to be 

 wrought carefully with fuie emery and a bruih ; and when it 

 is polifhed as high as can be by this means, it muft be wiped 

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

 egg. In this fort of work the operator mull always have 

 the caution to wear gloves, otherwife the Icall touch of the 

 aqua fortis will burn the fingers, and turn them yellow ; and 

 often, if it be not regarded, will eat off the Ikin and the 

 nails. 



Thefe are the methods to be ufed with fliells, which require 

 but a moderate quantity of the furface to be taken oft ; but 

 there are others which require to have a larger quantity taken 

 off, and to be uncovered deeper ; this is called entirely (caling 

 a (hell. This is done by means of an horizontal wheel ot 

 lead or tin, impregnated with rough emery ; and the fliell is 

 wrought down in the fame manner in which ftoncs are 

 wrought by the lapidary. Nothing is more difficult, how- 

 ever, than the performing this work with nicety ; very often 

 (hells are cut down too far by it, and wholly fpoiled ; and 

 to avoid this, a coarfe vein muft be often left Handing in 

 fome place, and taken down afterwards with the file, when 

 the cutting it down at the wheel would have fpoiled the ad- 

 jacent parts. 



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

 to be polilhed with fine emery, tripoli, or rotten ilonc, 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 fame ingredients, when a ftiell is full of tubercles, 

 or protuberances, which mutl be preferved. It is then im- 

 poffibleto ufethe wheel ; and if the common way of dipping 

 into aqua fortis be attempted, the tubercles, being harder than 

 the reft of the fhell, will be eat through before the reft is 

 fufBciently fcaled, and the (hell will be ipoiled ; in this cafe 

 induftry and patience arc the only means of effefting a polilh. 

 A camel's-hair pencil muft be dipped in aqua fortis, and 

 with this the intermediate parts of the (liell mull be wetted, 

 leaving the protuberances dry ; this is to be often repeated, 

 and after a few moments the (liell is always to be plunged 

 into water to (lop the erofion of the acid, which would other- 

 wife eat too deep, and dellroy the beauty of the" (hell. 

 When this has fufficiently taken off the foulncfs of the (hell, 

 it is to be polilhed with emery of the finell kind, or with 

 tripoli, by means of a fmall Hick, or the common polifhing 

 ftone of the goldfmiths may be ufed. 



This is a very tedious and troublefomc thing, efpecially 

 when the echinated oyllcrs and murices, and fome other 

 fuch (hells, are to be wrought ; and what is worll of all is, 

 that when all this labour has been employed, the bufinefs is 

 not well done ; for there ftill remain feveral places which 

 could not be reached by any inftrument ; fo that the fliell 

 muft neceflarily be rubbed over with gum-water, or the 

 white of an egg afterwards, in order to bring out the co- 

 lours, and give a glofs : in fome cafes it is even neceffary to 

 give a coat of varnifli. 



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

 lours, and add to the beauty of fliells ; and the changes 

 produced by polifhing in this manner are fo great, that the 

 (hell is often not to be known afterwards for the fame it 

 was ; and hence we hear of new (liells in the cabinets of 

 colleftors, which have no real exitlence as fcparatc fpccics, 

 but are the polKhed appearance of others well known. To 

 caution the reader againll errors of this kind, it may be 

 proper to add the moll remarkable fpecies thus ufually 

 altered. 



The onyx-(hell, or volute, called by us the purple or 



violet-tip, which in its natural ftate is of a fimple pale 

 brown, when it is wrought (lightly, or polilhed with juil 

 the fupcrficies taken off, is of a fine bright yellow ; and 

 when it is eat away deeper, it appears of a fine milk-white, 

 with the lower part blucifh : it is in this ftate that it is called 

 the onyx-fliell ; and it is preferved in many cabinets in its 

 rough ftate, and in its yellow appearance as different fpecies 

 of ihells. 



The violet-fhell, fo common among the curious, is a 

 fpecies of porcelain, or comm.on cowry, which does not ap- 

 pear in that elegance till it has been polifhed ; and the com- 

 mon auris marina (liews itfelf in two or three different forms, 

 as it is more or lefs deeply wrought. In its rough ftate it it 

 dullcy and coarfe, of a pale brown on the outfidc, and pearly 

 within : when it is eaten down a little way below the fur- 

 f icc, it (hews variegations of black and green ; and when 

 ftiU farther eroded, it appears of a fine pearly hue within 

 and without. 



The nautilus, wlien it is polilhed down, appears all over 

 of a fine pearly colour ; but when it is eaten away but to a 

 fmall depth, it appears of a fine yellowifti colour, with 

 dnn<y liairs. The burgau, when entirely cleared of its 

 coat, is of the moil beautiful pearl-colour ; but when only 

 digiitly eroded, it appears of a variegated mixture of green 

 and red : whence it has been called the parroquet-dicll. 

 The common lielmet-fhel!, when wrought, is of the colour 

 of the finell agate ; and the mufcles, in general, though 

 very plain fhclls, in their common appearance, become very 

 beautiful when polifhed, and fhew large veins of the moil 

 elegant colours. The Pcrfian fhell, in its natural Hate, is 

 all over white, and covered with tubercles ; but wlien it has 

 been ground down on a wheel, and polifhed, it appears of a 

 grey colour, with fpots and veins of a very bright and 

 highly polifhed white. The limpets, in general, become 

 very different when polifhed, moll of them (hewing very 

 elegant colours ; among thele the tortoife-fhell limpet is the 

 principal ; it does not appear at all of that colour or tranf- 

 parence, till it has been wrought. 



Tliat elegant fpecies of (hell called the junquil-chama, 

 which has deceived fo many judges of tliefe things into an 

 opinion of its being a new fpecies, is only a white chama, 

 with a reticulated furface ; but when this is polKhed, it 

 lofes at once its reticular work and its colour, and becomes 

 perfcdlly fmooth, and of a fine bright yellow ; and the 

 violet-coloured chama of New England, when worked 

 down and poliflied, is of a fine -.uilk-white, with a great 

 number of blue veins, difpofed like the variegations in 

 agates. 



The affes ear-fliell, when poliflied, after working it down 

 with the file, becomes extremely glofly, and obtains a fine- 

 lofe-colour all about the mouth. Thefe are fome of the 

 mofl frequent among an endlefs variety of changes wrought 

 on fliclls by poliftiing ; and we find there are many of the 

 very greateft beauties of this part f tiie creation wiiith 

 muft have been loft, but for tliis method of fearching deep 

 in the fubflance of the fticll for them. 



The Dutch are very fond of fliells, and are very nice in 

 their manner i)f working them : they are under no reftraint, 

 however, in their works, but ufe the moll violent methods, 

 fo as often to dillroy all the beauty of the fliell. They file 

 them down on all fides, and often take them to the wheel, 

 when it mnfl deflroy the very charjfters of the fpecies. 

 Nor do they Hop at tliis, but, determined to have beauty at 

 any rate, they are for improving upon nature, and frcqnently 

 add fome lines and colours with a pencil, afterwards cover- 

 ing them with a fine coat of varnilh ; Id tliat tliey Iceni the 

 natural liiieationi of the (hell. The Dutch tabincli arc by 

 3 P 2 thi« 



