138 Vegetable Physiology. ee 
8. That chlorous acid and ammonia can unite sdb — 
tion, but that the compound which they form, is changed by water into 
chlorine and azote. 
9. That the oxide of chlorine, obtained by the method of Stadion, 
is composed of one volume of chlorine and two volumes of OxyEeM 
and is the same as that obtained by Davy. 
10. That the chlorous acid may become a constituent part of an 
ether which is singularly disposed to a on into acetic 
ether.— Annales de Chim. et de Phys. Oct. 18 
Arr. asa tae egetable Physiology in relation to Least g : 
Crops; by M. Macarre. i 
Translated for this Journal by Pror. Siasacom. 
sindionte sabinindoned in the transactions of the Soeséeé: de Ee 
et Phistoire naturelle of Geneva, this gentleman has devek 
physiological facts, interesting to science and to practical voricule 
A judicious rotation of crops is known to be a matter of great im- 
portance. One kind of vegetable (A) will grow and flourish well in 
a soil from which another kind of vegetable (B) has just been gath- 
ered, while an attempt to raise another crop of the first vegetable (A); 
or a crop of a third vegetable (C) immediately after the first i 2 m 
the same soil will be attended with little or no success. The d 
ery of this fact which is almost as ancient as agriculture itself, aie 
posed to have led to the practice of fallowing. A piece of fallow 
ground will, almost toa certainty, be covered with a crop of 
These being plants of a different nature, do not unfit the soil, but 
prepare it for a succession of the same crop as that which preceded 
them. But science or experience has taught the enlightened farmer 
to substitute useful plants in the room of estore and thus kien 
grounds in profitable activity. 
Various reasonings have been employed to account fe the neces 
sity of this rotation. 1st. That different plants absorb different jaices 
from the same soil, and that a piece of ground exhausted by culture; 
may still be rich for. another ‘class of vegetables. But it is known 
to physiologists, that plants absorb all the soluble substances uae the 
soil contains, whether j injurious to their growth or not. 2d. the 
- roots of different plants being of different lengths, extend into differ 
ént layers of the soil, and thus derive from it appropriate nourishment. 
