SHALES AND MINERAL OILS 765 



of forms to suit it to the various purposes to which it is now applied. We find it 

 in almost every large manufactory ; and in nearly every family, the hand-sewing 

 machine has its place. 



SHADDOCK. The fruit of the Citrus decumana, which is much cultivated in the 

 West Indies. It is sold in this country as the ' Forbidden Fruit.' 



SHAFT, in mining, signifies a perpendicular or slightly-inclined pit. See 

 MININO. 



SHAGRZSXjXQT. (Chagrin, Fr. ; Schagrin, Ger.) The true oriental shagreen is essen- 

 tially different from all modifications of leather and parchment. It approaches the 

 latter somewhat, indeed, in its nature, since it consists of a dried skin, not combined 

 with any tanning or foreign matter whatever. Its distinguishing characteristic is 

 having the grain or hair side covered over with small rough round specks or 

 granulations. 



It is prepared from the skins of horses, wild asses, and camels ; of strips cut along 

 the chine, from the neck towards the tail, apparently because this stronger and 

 thicker portion of the skin is best adapted to the operations about to be described. 

 These fillets are to be steeped in water till the epidermis becomes loose, and the hairs 

 easily come away by the roots ; after which they are to be stretched upon a board, 

 and dressed with the currier's fleshing-knife. They must be kept continually moist, 

 and extended by cords attached to their edges, with the flesh-side uppermost upon 

 the board. Each strip now resembles a wet bladder, and is to be stretched in an 

 open square wooden frame by means of strings tied to its edges, till it be as smooth 

 and tense as a drum-head. For this purpose it must be moistened and extended from 

 time to time in the frame. 



The grain or hair-side of the moist strip of skin must next be sprinkled over 

 with a kind of seed called Allabuta, which are to be forced into its surface either 

 by tramping with the feet, or with a simple press, a piece of felt or other thick 

 stuff being laid upon the seeds. The seeds belong probably to the Chenopodium 

 alburn. They are lenticular, hard, of a shining black colour, farinaceous within, 

 about the size of a poppy-seed, and are sometimes used to represent the eyes in wax 

 figures. 



The skin is exposed to dry in the shade, with the seeds indented into its surface ; 

 after which it is freed from them, by shaking it, and beating upon its other side with 

 a stick. The outside will be then horny, and pitted with small hollows corresponding 

 to the shape and number of the seeds. 



In order to make the next process intelligible, we must advert to another analogous 

 and well-known operation. When we make impressions in fine-grained dry wood 

 with steel punches or letters of any kind, then plane away the wood till we come to 

 the level of the bottom of these impressions, and afterwards steep the wood in water, 

 the condensed or punched points will swell above the surface, and place the letters in 

 relief. Snuff-boxes have been sometimes marked with prominent figures in this way. 

 Now shagreen is treated in a similar manner. 



The strip of skin is stretched in an inclined plane, with its upper edge attached to 

 hooks and its under one loaded with weights, in which position it is thinned off with a 

 proper semi-lunar knife, but not so much as to touch the bottom of the seed-pits or 

 depressions. By maceration in water, the skin is then made to swell, and the pits 

 become prominent over the surface which had been shaved. The swelling is com- 

 pleted by steeping the strips in a warm solution of soda, after which they are cleansed 

 by the action of salt-brine, and then dyed. 



In the East the following processes are pursued. Entirely white shagreen is 

 obtained by imbuing the skin with a solution of alum, covering it with the dough 

 made with Turkey wheat, and after a time washing this away with a solution of alum. 

 The strips are now rubbed with grease or suet, to diminish their rigidity, then worked 

 carefully in hot water, curried with a blunt knife, and afterwards dried. They are 

 dyed red with decoction of cochineal or kermes, and green with fine copper-filings 

 and sal-ammoniac, the solution of this salt being first applied, then the filings being 

 strewed upon the skin, which must be rolled up and loaded with weights for some 

 time ; blue is given with indigo, quicklime, soda, and honey ; and black, with galls 

 and copperas. 



Shagreen is also prepared from the skin of the shark. 



SHAXiES AND MINERAIi OIKS. Shale, according to old writers on pet- 

 rology, signifies any rock, no matter of what mineral composition, splitting into thin 

 laminae, and found in what they termed the secondary and tertiary formations. Schist 

 was the distinguishing appellative of such rocks splitting up in thin layers, found in 

 the primitive formations of the same authors. The characteristic features of the in- 

 dividual rock were usually prefixed. Thus such terms as mica-schist, talc-schist, alum- 

 shale, argillo-bituminous shale. &c,, originated. But though they are still retained, a 



