142 ON HUMAN HAIR. 



same object, carefully observing the phenomena that 

 occur, and meditating on the causes that have produced 

 them, that we arrive at results, which it was impossible to 

 have foreseen a priori. He does not flatter himself, 

 however, that he has penetrated all the secrets of Nature 

 in this respect, and he offers his ideas with that diffidence 

 which we ought to feel in researches of such difficulty. 

 But he gives an accurate description of his experiments : 

 he compares them, discusses them, and draws from them 

 these conclusions, that appear to him most natural. Of 

 the principal of these experiments, and the corollaries he 

 deduces from them, we shall give a concise account. 

 Hair boiled J ])oiled hairs in water for several days, says Mr. Vau- 



^ quelin, without being able to dissolve them; yet the 



water contained a small quantity of animal matter, as 

 was demonstrated by nut-galls and other reagents. 



It is probable, that this matter, which imparts to water 



the property of becoming putrid, is foreign to the sub* 



is not dissolved stance of the hair itself. From this experiment I infer, 



that at the temperature to which water can be raised un* 



der the pressure of the atmosphere alone, hair is not 



soluble in it* 



Dissolved in a I effected their solution, however, without any altera- 



close vessel, ^^^^ ^^ Papin's digester, by regulating the degree of heat. 



In this operation, if the heat be carried beyond a cer- 



but decompos- ^^^^ point, the hair will be wholly or partly decomposed; 



edintoostronifasisshewn by the ammonia, carbonic acid, and empyreu- 



a heat. matic fetid oil, which is found ki the solation? to which 



the oil imparts a deep yellow colour. 



Sulphurated ^^ either case a large quantity of sulphurated hidrogeu 



hidrogen gas is evolved, which acts strongly on the sides of the 



cvovc, copper vessel, turning them black. More is found if the 



perhaps form- heat be raised to a higher degree, which seems to indicate, 



cd during the that this matter,is produced during the operation. 



BlaclThair af- ^^ *^*^ ^^^^ employed were black, or if the heat were 



fords a black not sufficiently high to decompose the hair, a black mat* 



residuum; ^^^ remains, which falls down very slowly, in consequence 



of its minute division and the consistence of the solution. 



This substance is composed chiefly of a black oil, as 



thick as a bitumen, a little^ soluble either in alcohol or 



^Icalis, with iron and sulphur perhaps united together. 



RecJ 



