When the experimenter is become acquainted 
with the use of the different instruments, the pro- 
perties of the re-agents, and the relations between 
the external and chemical qualities of soils, he will 
seldom find it necessary to perform, in any one 
case, all the processes that have been described. 
When his soil, for instance, contains no notable 
proportion of calcareous matter, the action of the 
muriatic acid (7) may be omitted. In examining 
peat soils, he will principally have to attend to the 
operation by fire and air (8) ; in the analysis of 
chalks and loams, he will often be able to omit the 
experiment by sulphuric acid (9) ; and when a 
soil is extremely dense and heavy, and after being 
heated to redness, strongly attracted by the magnet, 
he must particularly attend to the quantity of 
iron it contains ; and, in this case, the muriatic acid 
will be the principal agent. 
In the first trials that are made by persons un- 
acquainted with chemistry, they must not expect 
much precision of result. Many difficulties will 
be met with ; but in overcoming them, the most 
useful kind of practical knowledge will be ob- 
tained; and nothing is so instructive in experi- 
mental science as the detection of mistakes. The 
correct analyst ought to be well grounded in gene- 
ral chemical information ; but, perhaps, there is no 
better mode of gaining it, than that of attempting 
original investigations. In pursuing his experi- 
ments, he will be continually obliged to learn the 
properties of the substances he is employing or 
acting upon ; and his theoretical ideas will be 
more valuable in being connected with practical 
