ion, and facts will soon cluster and cling to him like grapes to
their stem. Their relations to the theory will hold them fast; and, the
more of these the mind is able to discern, the greater the erudition
will become. Meanwhile the theorist may have little, if any, desultory
memory. Unutilizable facts may be unnoted by him, and forgotten as soon
as heard. An ignorance almost as encyclopedic as his erudition may
coexist with the latter, and hide, as it were, within the interstices of
its web. Those of you who have had much to do with scholars and
_savants_ will readily think of examples of the class of mind I mean.

The best possible sort of system into which to weave an object,
mentally, is a _rational_ system, or what is called a 'science.' Place
the thing in its pigeon-hole in a classificatory series; explain it
logically by its causes, and deduce from it its necessary effects; find
out of what natural law it is an instance,--and you then know it in the
best of all possible ways. A 'science' is thus the greatest of
labor-saving contrivances. It relieves the memory of an immense number
of details, replacing, as it does, merely contiguous associations by the
logical ones of identity, similarity, or analogy. If you know a 'law,'
you may discharge your memory of masses of particular instances, for the
law will reproduce them for you whenever you require them. The law of
refraction, for example: If you know that, you can with a pencil and a
bit of paper immediately discern how a convex lens, a concave lens, or a
prism, must severally alter the appearance of an object. But, if you
don't know the general law, you must charge your memory separately with
each of the three kinds of effect.

A 'philosophic' system, in which all things found their rational
explanation and were connected together as causes and effects, would be
the perfect mnemonic system, in which the greatest economy of means
would bring about the greatest richness of results. So that, if we have
poor desultory memories, we can save ourselves by cultivating the
philosophic turn of mind.

There are many artificial systems of mnemonics, some public, some sold
as secrets. They are all so many devices for training us into certain
methodical and stereotyped _ways of thinking_ about the facts we seek to
retain. Even were I competent, I could not here go into these systems in
any detail. But a single example, from a popular system, will show what
I mean. I take the