Silk Manufacture. 309 



small balloons, which were far more permanent than any formed 

 of soap and water, and which equally exhibited the prismatic 

 colors. The texture of these bladders w^as so tenacious, as to 

 render them impervious to the most subtle gas. Chappe filled 

 several of them, whose diameter did not exceed three inches, 

 with hydrogen gas, and the little air balloons remained unbroken 

 and floating in his apartment for considerably more than twenty- 

 four hours. All cocoons are not sufficiently glutinous for this 

 purpose ; with those which are of a very deep yellow the exper- 

 iment will not succeed : such are supposed to be produced by 

 the worm in a peculiar state of disease, which state is yet by no 

 means uncommon. 



' According to Westrum, silk, when acted upon by chlorine, 

 either in the gaseous form or diluted in water, instead of being 

 bleached, as cotton or hnen would be, always becomes of a yel- 

 low color, and loses part of its sohdity. The caustic alkalies cor- 

 rode and dissolve silk, which give by distillation the results 

 usual with animal substances. 



' Neumann found that but few materials afforded an equal quan- 

 tity of volatile alkali. Tournefort observes that it contains more 

 than hartshorn, as he obtained from fifteen ounces of silk two 

 drachms of volatile salt : this, which was called the spirit of raw 

 silk, when rectified with some essential oil, was the medicine 

 formerly celebrated under the name of " Guttae Anglicans, " or 

 English drops. The volatile alkali obtained from silk was then 

 supposed to be of a different nature from that contained in any other 

 substance, and it consequently was held to possess different virtues 

 pecuhar to itself. So salt of tartar, and sub-carbonate of potass, 

 w^ere for a long time considered to be, and were, used as two 

 separate substances. The chemical philosopher had not then 

 learned to generalize, and could not understand that the same 

 substance, differing in no one pailicular as to its nature and prop- 

 erties, could be obtained from many apparently wholly dissimilar 

 bodies. 



' Before the discoveries of chemistry had arrested the fanciful 

 flights and annihilated the quaint distinctions of the druggist, his 

 catalogue presented a curious nomenclature, which is now ac- 

 knowledged to have been founded on ignorance and prejudice. 

 The light of science has since pierced the veil, and has revealed 

 many of the laws of nature in all the beautiful simplicity of their 

 elements ; dispelling much of the complicated mystery and vague 

 obscurity which then enveloped the ill-understood practice of 

 pharmacy. 



' A silk covering of the texture of a common handkerchief is 



