51 
Water consists of two proportions of hydrogene 
and one of oxygene 15 ; and when water unites 
to other bodies in definite proportions, the quantity 
is 17, or some multiple of 17, i. e* 34 or 51, or 68, 
See. 
Soda , or the mineral alkali, contains two propor- 
tions of oxygene to one of sodium. 
Ammonia , or the volatile alkali, is composed of 
six proportions of hydrogene and one of azote. 
Amongst the earths, Silica, or the earth of 
flints, probably consists of two proportions of 
oxygene to one of silicon ; and Magnesia , Sir on- 
tia, Baryta, or Barytes, Alumina , Zircona , Glu- 
cina , and Ittria, of one proportion of metal and 
one of oxygene. 
The metallic oxides in general consist of the 
metals united to from one to four proportions of 
oxygene; and there are, in some cases, many 
different oxides of the same metal ; thus there are 
three oxides of lead; the yellow oxide, or mas- 
sicot, contains two proportions of oxygene; the 
red oxide, or minium, three ; and the puce-coloured 
oxide four proportions. Again, there are two 
oxides of copper, the black and the orange ; the 
black contains two proportions of oxygene, the 
orange one. 
For pursuing such experiments on the compo- 
sition of bodies as are connected with agricultural 
chemistry, a few only of the undecompounded 
substances are necessary; and amongst the com- 
pounded bodies, the common acids, the alkalies, 
and the earths, are the most essential substances. 
The elements found in vegetables, as has been 
E 2 
