tanning Principle , and gallic Acid , in the Bark of Trees. 263 
SCALE OF BARKS. 
Gallic acid, 
Tanning prin- 
Tanning princi- 
ple, (in grains,) 
from half a pint 
of infusion and an 
Bark of 
by colour. 
drometer. 
ounce of s 
of glue. 
Elm* - 
7 
2,1 
28 
Oak, cut in the winter 
8 
2,1 
3 ° 
Horse chesnut - 
6 
2,2 
3 ° 
Beech - 
7 
2,4 
3 i 
Willow (boughs) 
- 8 
2,4 
3 i 
Elder - 
4 
3 >° 
41 
Plum-tree 
8 
4 >° 
58 
Willow (trunk) - 
9 
4 >° 
52 
Sycamore - 
6 
4 A 
S3 
Birch - 
• 4 
4 M 
5 4 
Cherry-tree - 
8 
4 > 2 
59 
Sallow ----- 
8 
4 > 6 
59 
Mountain ash - 
8 
4 >7 
60 
Poplar - - - - - 
8 
6 , 0 
76 
Hazel - 
9 
6 >3 
79 
Ash - 
10 
6,6 
82 
Spanish chesnut - 
10 
9>o 
98 
Smooth oak - 
10 
9,2 
104 
Oak, cut in spring 
10 
9> 6 
108 
Huntingdon or Leicester willow 
10 
10,1 
109 
Sumach - - - - 
14 
16,2 
158 
* The infusion of elm was so loaded. with mucilage, that it was with difficulty 
could separate the tanning principle, or try the specific gravity. 
Mm2 
