" None are found to make such gross mistakes, or to fall into so great absurdities, as those who try to learn without trouble, and by the mere hasty perusal of philosophical works.

The various branches of experimental science are intimately con- nected, and serve, often, to explain each other.

Hence, numerous references will be found in the following work: and, by means of them, a fact or a principle, that may have been forgotten, can be easily recalled to memory.

Popes Essay on Criticism.

Since the different sciences "are thus made to illustrate one another, each will be found to have been, in reality, treated at much greater length than might, at first, be supposed from the size of the volume.