SILK. 



fuch fale to be to the king, and Iialf to the officer wlio fhall 

 feize and feciire the fame ; and the fame goods (hall not be 

 dehvered out of the warehoufe, till fecurity fhall be given 

 for exportation, and that the fame fhall not be landed again 

 in any part of his majefty's dominions. 



By 5 Geo. III. c. 48, if any foreign manufaftured filk- 

 ftocking?, filk-mitts, or iilk-gloves, Ihall be imported into 

 this kingdom, or any part of the Britifh dominions, the 

 fame (liall be forfeited, and liable to be fcarched for and 

 feized as other uncuflomed goods ; and every perfon who 

 fhall import the fame, or be affiiling therein, and the ven- 

 ders and retailers in whofe cuilody they fhall be found, or 

 who (hall fell or expofe the fame to fale, or conceal with 

 intent to prevent the forfeiture, fhall, over and above the 

 forfeiture of the goods, forfeit 200/., with cofls ; half to 

 the king, and half to the officer who fhall inform and pro- 

 fecute. 



And when the goods feized (being out of the limits of 

 the bills of mortality) fliall not exceed the value of 20/., 

 two juftices may proceed to the condemnation thereof. 

 And the proceedings, in all other refpeft-, fliall be in like 

 manner as in the cafe of ribbands and laces above men- 

 tioned. 



Silk, in Chemiflry, deferves notice on account of a pe- 

 culiar fait, or cryltalline fubllance, obtained from it by the 

 nitric acid. In its natural ftate, or before it is bleached, it 

 contains a yellow refinous matter, from which it derives its 

 fine golden colour. When raw lilk is infufed in water, a 

 portion of gummy matter is dillolved, and a light amber- 

 coloured liquor is produced. Pure alcohol extrafts a much 

 deeper yellow colour, and makes a tincture, that lofes none 

 cf its colour by long expofure to the fun, which bleaches 

 the filk itfelf. Nitrous acid aifts powerfully on iilk, in 

 proportion to its concentration. If two drachms of this 

 acid are mixed with a pint of alcohol, and filk, either raw 

 or bleached, be immerfed in it, and kept in digeftion, in a 

 moderate warmth, for twenty-four hours, the hlk becomes 

 of a dull yellowifh-brown, which, after rinfing and wafliing 

 with foap, and drying, turns to a fine golden yellow, which 

 is very permanent. But when concentrated nitric acid is 

 diftiUed off filk, and the remaining liquor duly evaporated, 

 much oxalic acid is obtained ; and the refidue, if evaporated 

 ftill further, yields, together with a little remaining oxahc 

 acid, a quantity of yellow granular cryftals, very bitter, 

 not acid, and ftaining the faliva and hands of 1 very deep 

 yellow, not eafily removed. If the liquor is previoufly 

 laturated with pctafh, and evaporated, another yellow 

 filky fait evaporates, which detonates on coals like common 

 nitre, and appears to be a triple combination of the former 

 bitter fubllance with nitrate of potafh. The firit mentioned 

 granular cryftals, examined with a magnifier, appear to be 

 compofed of truncated odlohedrons. 



The above curious fubftance was difcovered by Welter, 

 and called by him the " bitter priliciple." He fuppofes it 

 to be generally produced by tlie adtion of nitric acid on 

 animal matters ; and it is perhaps the fame fubftance which 

 caufes the bitterr.cfs of bile. Aikin. 



The fpirit of raw filk, rc-flified with fome efTential oil, is 

 the medicine commcidy known by the name of Guttit An^li- 

 cane, or Englifh drops. 



Silk, Spider. Within about a century the fecret has been 

 found in France, of procuring and preparing filk from the 

 webs of fpiders ; and the ufing it in leveral manufaftures has 

 been attempted. This difcovery is owing to M. Bon, in 

 1 7 10, who publlfhed a diflertatioQ on the fubjeft, whence 

 what follows is extrafted. 



Spiders are ufually diftinguifhed, either \vith regard to 

 their colour, as into black, brown, yellow, white, &c. or 

 with regard to the number, or arrangement, of their eyes ; 

 fome having fix, others eight, others ten. But with regard 

 to the filk-fpiders, M. Bon reduces tiiem all to two kinds ; 

 thofe with long legs, and thofe with Hiurt : which laft are 

 thofe which fumilh the finefl raw filk. The filk-fpider 

 makes a filk every whit as beautiful, gloffy, and ftrong, as 

 the filk-worm : it fpins it from the anus ; around which are 

 five papillae, or fmall nipples ; and behind thefe, two others, 

 all mufculous, and furnifhed with fphinftcrs. Thefe nipples 

 ferve as fo many wire-drawing irons, to form and mould a 

 vifcous liquor, which, when dried in the air, after being 

 drawn through them, makes tlie filk. Each of thefe nipples, 

 M. Reaumur obferves, confitts of a number of lefs and in- 

 fentible ones ; which one may be convinced of by prcfiing 

 a fpider's belly between the fingers, to oblige the hquor to 

 flow into the nipples ; for by this means, applying the finger 

 ?.gainft the anus, feveral diliindl threads will be drawn out 

 through the feveral perforations of each nipple. The 

 threads are too fine to be counted with any certainty ; but 

 M. Reaumur reckons each larger nipple may fend forth a 

 great many. 



Hence we fee how the fpiders make their threads biggei* 

 or fmaller : for as, before they begin to fpin, they always 

 apply more or fewer of thefe nipples againft the body 

 whence the web is begun ; or, as they apply each more or 

 lefs ftrongly ; fo, as more or fewer of the minuter nipples 

 come to take, the thread thus fpun will be a compound of 

 more or fewer of the finglc threads. Indeed, as the threads 

 come from the anus all joined together, they appear to be 

 fingle ; but M. Ben has diftinguifhed one of the fingle ones 

 to confiil of fifteen or twenty diftinft threads. 



The threads are of two kinds : the firft is weak, and only 

 ferves for that kind of web with which they catch flies. 

 The fecond is much flronger, and ferves to wrap up therr 

 eggs in ; which, by this means, are fheltered from the cold, 

 as well as from infccls, which might otherwife gnaw and 

 dellroy them. Thefe threads they wind very loofely round 

 the eggs, refcmbliiig the balls or bags of iilk-worms, that 

 have been prepared and loofened for the diftaff. 



The fpider-bags are of a grey colour, when new ; but 

 they turn blackifh, when long expofed to the air: indeed, 

 one might find other fpiders' bags of other colours, and 

 which would afford a better filk ; but the'r fcarcity would 

 render the experimei.t difficult : for which reafon, we con- 

 fine ourfelves to the bags of the m.ofl common fpiders, which 

 are the fhort-legged kind. Thefe always find out fom« 

 place, fecure from the wind and rain, to make their bags ; 

 as hollow trees, the corners of windows, or vaults, or under 

 the eaves of houfes. 



By coUefting a quantity of thefe bags, a new filk is made, 

 inferior in nothing to the common filk. It takes all kinds 

 of dyes, and may be made into all kinds of ftuffs. M. Bon 

 had ilockings and gloves made of it, which he prefented to 

 the Academy, and others to our Royal Society. 



For the manner of preparing the bags to get the filk, it 

 is thus: after having gathered twelve or thivteen ounces 

 of thefe bag?, M. Bon had them well beaten for fome time, 

 with the hand, and a flick, to get out all the dull ; he then 

 wafhed them in lukewarm water, till they left the water 

 very clean : after this, he laid them to fleep, in a large 

 veffel, with foap, and faltpetre, and gum arabic. The 

 whole was left to boil, over a gentle fire, for three hours. 

 The bags were next wafhed in warm water, to get out 

 the foap J and after all, laid to dry fome days, to fit then> 



for 



