face of the copper, or by rendering it negative, it allowed marine
animals and vegetables to accumulate on its surface, and thus impede the
progress of the vessel.]

Other instances might, if necessary, be adduced, to show that long
intervals frequently elapse between the discovery of new principles
in science and their practical application: nor ought this at all to
surprise us. Those intellectual qualifications, which give birth to new
principles or to new methods, are of quite a different order from those
which are necessary for their practical application.

At the time of the discovery of the beautiful theorem of Huygens,
it required in its author not merely a complete knowledge of the
mathematical science of his age, but a genius to enlarge its boundaries
by new creations of his own. Such talents are not always united with a
quick perception of the details, and of the practical applications
of the principles they have developed, nor is it for the interest of
mankind that minds of this high order should lavish their powers on
subjects unsuited to their grasp.

In mathematical science, more than in all others, it happens that truths
which are at one period the most abstract, and apparently the most
remote from all useful application, become in the next age the bases
of profound physical inquiries, and in the succeeding one, perhaps, by
proper simplification and reduction to tables, furnish their ready and
daily aid to the artist and the sailor.

It may also happen that at the time of the discovery of such principles,
the mechanical arts may be too imperfect to render their application
likely to be attended with success. Such was the case with the principle
of the hydrostatic paradox; and it was not, I believe, until the
expiration of Mr. Bramah's patent, that the press which bears his
name received that mechanical perfection in its execution, which has
deservedly brought it into such general use.

On the other hand, for one person who is blessed with the power of
invention, many will always be found who have the capacity of applying
principles; and much of the merit ascribed to these applications will
always depend on the care and labour bestowed in the practical detail.

If, therefore, it is important to the country that abstract principles
should be applied to practical use, it is clear that it is also
important that encouragement should be held out to the few who
are capable of adding to the number of those