points out the countries and climates which different 
families affect ; and gives us principles for their cultivation, 
either as medicines, or as objects of agriculture : the other 
is no less valuable in affording us innumerable indications in 
every part of the world, for discovering the properties of 
new and unknown plants, whether as fitting them for food, 
for medicine, or for any of the arts of life ; and though 
there are no doubt exceptions, (fewer, however, than 
usually adduced) there certainly is no other method by 
which we may so readily find a substitute for a medicine, 
or an equivalent for an article of trade, as by seeking for it 
in the families of plants, which are already known to 
contain some possessed of such properties as we desiderate. 
This is no trivial advantage ; for though our Pharma- 
copoeias and Dispensatories may be models of what is 
requisite for civilized society, yet if it be considered that 
the English Schools of Medicine supply practitioners for 
an empire, on which, without hyperbole, it has been said, 
the sun never sets ; it will readily be allowed, that we may 
frequently be placed where there are neither chemists to 
analyse, nor herbalists to select the plants, secreting most 
valuable products at our feet; but to which we might 
readily be led by studying their natural affinities. Our 
systems of Materia Medica might therefore inculcate these 
more comprehensive doctrines, and a teacher extend the 
range of his influence and usefulness, while describing any 
officinal species, by introducing it with general observations 
on the family to which it belongs, as well as the countries 
where this is chiefly found. An Indian sage, after giving 
a prescription of precious stones, for curing the diseases of 
kings and rich men, very judiciously adds another, for 
people in general, composed of vegetables, because these 
are procurable by all. 
The system of arrangement, however, alone applicable 
