82 COSMETICS. 



paration of silver, blackens when exposed to air and light; 

 accordingly the number of silver preparations which from 

 first to last have been employed as indelible inks and as hair- 

 dyes is very great. I need not specify them here. To one 

 and all the defect attaches of not only dyeing the hair, but 

 everything they come in contact with. The nails, the skin, 

 even the teeth if it should happen to touch them, are dyed 

 black by nitrate of silver, and other silver solutions. This is 

 a serious defect, but it does not stand alone. If the surface 

 of a piece of bone or ivory the handle of a tooth-brush, for 

 example be dyed black with nitrate of silver, and continu- 

 ously exposed to light, a coat of metallic splendour will at 

 length become apparent, mingled with iridescent hues like 

 the tints on the neck of a dove. This chromatic play of tints 

 is very beautiful, in suitable places and under proper circum- 

 stances. It is out of place when seen in the human hair ; 

 yet I could specify the moustache and whiskers of certain old 

 .gentlemen known to me, whereon that silvery splendour and 

 those dove-like tints may be seen in much perfection. 



Accordingly, notwithstanding the convenience of its ap- 

 plication, solutions of silver cannot be recommended as hair- 

 dyes, and consequently they have much gone out of vogue. 

 A hair-dye, to be as good as it can be, should have the pro- 

 perty of dyeing the hair alone, leaving the skin untouched. 

 This can be accomplished by the use of some one amongst 

 many metallic solutions, and the rationale is explicable on 

 grounds of physiological chemistry. First, it is needful to 

 state that nearly all the ordinary or calcigenous metals when 

 dissolved yield solutions that are blackened by the contact 

 of sulphuretted hydrogen gas, a compound holding sulphur. 

 Secondly, it is needful to state that the element sulphur is a 

 constituent of hair, which continually evolves, but more espe- 

 cially during sleep, the gas in question. We now begin to 

 perceive what must come to pass if we moisten hair with the 

 solution of one of the metals capable of blackening under the 



