ym 
at 
92 On Plaister of Paris. . 
assist and promote the growth of plants.(p) Perhaps 
(p )Ingenhausz a celebrated advocate for the new chemis- 
try, o. which Mons. Lavoisier was the sounder, has, this year, 
(1796) published ‘+ an essay on the food o/ plants, and reno- 
vation of soils.” He imagines wonderiul effects may be pro- 
duced by oil.oi vitriol (or any concentrated acid, much dilu- 
ted with water, or mixed with earth) poured on the soil 
immediately be‘ore sowing. The cost of this manure about 
two shillings sterling per acre. He relates some experiments 
on a small scale, ‘confirmatory of this hypothesis, but ac- 
knowledges it now to ‘be mere theory. His opinion, and 
that o; others cited by him, 's, that xed air, now cailed, in the 
new nomenclature, carbonic acid, (‘rom its being jound plen- 
tifully in chalk, it is also called cretacious acid) is, in a great 
degree, the !ood o: plants. He asserts, in oppos-tion to Dr. 
Priestly and others, that plants thrive the best in oxygen 
or vital air; or at least cannot live without it. His theory, 
which is among the most modern, is, that carbone (charcoal) 
though oi itseli no manure, is the foundation oi the ‘ood of 
plants; but must be mixed with oxygen or vital air. Plants, 
according to this theory, decompose the air surrounding 
them; and, by this process, assist in producing their own ‘ood. 
That this process is perorming at all times, by the roots 
and flowers, but is carried on by the leaves and_ stalks in 
the night, or shade, and inhaled by the latter in the cooler 
parts oi the day; but constantly ‘rom the earth (where it 
is chiefly deposited) by the roots. That plants accelerate 
their growth im the dark, and advance the least in the 
middle of the day. That they possess the power of shifting 
carbonic acid irom the air, by attracting its oxygen, and 
furnishing it with carbon; and that they also possess a 
wonder:ul faculty of changing water into oxygen or vital 
air. That the oxygen is also acquired from the common 
