129 
So that a fourth part of the weight of the potatoe 
at least may be considered as nutritive matter. 
Mr. Knight informs me, that he has found the best 
potatoes, such as the Irish apple, to possess much 
greater specific gravity than the inferior varieties ; 
the specific gravity varying from 1075 to 1100, 
and it is probable that their nutritive properties are 
nearly proportionate to their specific gravities. 
The turnip, carrot, and parsnip, afford princi- 
pally saccharine, mucilaginous, and extractive 
matter. I obtained from 1000 parts of common 
turnips 7 parts of mucilage, 34 of saccharine mat- 
ter, and nearly 1 part of albumen. 1000 parts of 
carrots furnished 95 parts of sugar, 3 parts of 
mucilage, and ^ part of extract ; 1000 parts of 
parsnip afforded 90 parts of saccharine matter, and 
9 parts of mucilage. The Walcheren or white 
carrot , gave, in 1000 parts, 98 parts of sugar, 2 
parts of mucilage, and 1 of extract. 
Fruits, in the organization of their soft parts, 
approach to the nature of bulbs. They contain a 
certain quantity of nourishment laid up in their 
cells for the use of the embryon plant ; mucilage, 
sugar, starch, are found in many of them often 
combined with vegetable acids. Most of the fruit 
trees common in Britain have been naturalized on 
account of the saccharine matter they contain, 
which, united to the vegetable acids and mucilage, 
renders them at once agreeable to the taste, and 
nutritive. 
The value of fruits for the manufacture of fer- 
mented liquors may be judged of from the specific 
gravity of their expressed juices ; but the quantity of 
K 
