40 
connection of magnetism and electricity is of 
recent discovery, and the fact which served to esta- 
blish it was made known by M. CErsted, a Danish 
philosopher. It will ultimately probably tend to a 
more intimate acquaintance with the nature of 
these two extraordinary agents. The attractive 
powers of the magnet may be made use of to show 
the existence of iron in soils, as will be mentioned 
more particularly hereafter. 
The different powers that have been thus 
generally described continually act upon common 
matter so as to change its form, and produce 
arrangements fitted for the purposes of life. 
Bodies are either simple or compound. A body is 
said to be simple, when it is incapable of being 
resolved into any other forms of matter. Thus, 
gold or silver, though they may be melted by heat, 
or dissolved in corrosive menstrua, yet are re- 
covered unchanged in their properties, and they 
are said to be simple bodies. A body is considered 
as compound, when two or more distinct sub- 
stances are capable of being produced from it: thus 
marble is a compound body, for by a strong heat 
it is converted into lime, and an elastic fluid is 
disengaged in the process ; and the proof of our 
knowledge of the true composition of a body is, 
that it is capable of being reproduced by the same 
substances as those into which it had been decom- 
posed ; thus, by exposing lime for a long while to 
the elastic fluid, disengaged during its calcination, 
it becomes converted into a substance similar to 
powdered marble. The term element has the 
same meaning as simple or undecompounded body ; 
but it is applied merely with reference to the pre- 
