224 Mr. Hatchett on an artificial tanning Substance « 
whether vegetable, animal, or mineral, to the action of nitric 
acid. 
Since the preceding experiments were made, I have farther 
proved the efficacy of this substance by actual practice, and 
have converted skin into leather by means of materials which, 
to professional men, must appear extraordinary, such as, deal 
saw-dust, asphaltum, common turpentine, pit-coal, wax candle, 
and a piece of the same sort of skin. 
Allowing, therefore, that the production of this substance 
must for the present be principally regarded only as a curious 
chemical fact not altogether unimportant, yet as the principle 
on which it is founded appears to be developed, we may hope, 
that a more economical process will be discovered, so that 
every tanner may be enabled to prepare his leather even from 
the refuse of his present materials. 
The organized bodies and their products have only of late 
years much attracted the attention of chemists, many of whom, 
even at this time, ( although the modes of chemical examina- 
tion have been so much improved,) seem disgusted and 
deterred by the Proteus-like changes which take place when- 
ever these substances are subjected to experiment. 
But these variable and endless alterations of their properties 
seem rather calculated to operate as incitements to investi- 
gation; for by the accumulation of facts resulting from the 
changes produced in these bodies by disuniting and by re- 
combining their elementary principles, not only will chemistry 
as a science become farther illumined and extended, but it 
will, as it has hitherto done, render great and essential services 
to the arts and manufactures. 
