of its different States on Dyeing. 47 



and dwindling- to nothing in those of the same species that 

 are covered with hair, as the sheep of Guinea and Senef;;al ? 



As M. Board cannot at present give his observations all 

 the latitude of which they are susceptible, he hastens to 

 make public the experiments relative to the eficcts produced 

 jn dyeing by the difilient qualities of the wools he em- 

 ployed. 



The colour assumed hy wools while steepino- appeared to 

 him a fact so interesting, that he thought it necessary to 

 investigate the cause. He alternately changed the vessels 

 and the agents destined for this operation, and ascertained 

 that this coloration ought to be ascribed entirely to the ac- 

 tion of copper; for ammonia forms a blue precipitate in 

 steeping vessels of that metal, while the same precipitate 

 is extremely white, if vessels of earth, porcelain, or even tin, 

 be employed. Wool left fen- some hours in boiling water, 

 in a copper vessel, acquires a greenish gray tint; but this 

 effect is greatly augmented by the ordinary mixture of alum 

 and tartar. If into this bath, saturated and boilino:, you 

 plunge different kinds of combed wool, those prodiiced by 

 the native breed of France and Holland assume a lively 

 green colour, and those of Merinos a oreenish yellow, or a 

 very dark ochre yellow. 71-iough this ef^isct is much less 

 perceptible in steeps on a large scale, yet, bv comparing 

 white wool with that which has been steeped, the diflercncc 

 appears sufficiently striking. Tlie colour fixed by this me- 

 thod is very little altered by alkalies, and not at all by acids, 

 which in a slight degree heighten its intensity: ammonia 

 turns it to a yellowish grav. 



In these experiments the author employed alum manu- 

 factured by M. Curaudau, which appeared to him to possess 

 all the qualities and defects of Roman alum, in a compara- 

 tive investigation which he undertook relative to the eftects 

 in dyeing of all the kinds sold in the shops. 



Tiie wo(jl3, after remaining eight days in the alum liquor, 

 were then dyed with cochineal, madder, saunders wood, 

 &c. The same qualities, whether natural or acquirec, 

 having appeared to act in the same, manner in all the expe- 

 riments to v.hich they were subjected, M. Roard describes 

 only the first, v\liich was that made with cochineal. 

 Experiment I. 

 Ko. I. Healthy Merinos. 



A beautiful carnation red, inclining a little to a-pIIow. 

 This No. 1. surpassed in depth and intensity all the shades 

 which he tried of more than two or three colpurs. 



l:^xpcrimcat 



