Now, as to transportation by _water_, I have concluded, without sufficient authority perhaps, to use the term “boat” as a general name for all water-craft. The boat is indispensable to navigation. It is not probable that the philosophical principle upon which the use of the boat primarily depends--to-wit, the _principle_, that anything will float, which cannot sink without displacing more than its own _weight_ of water--was known, or even thought of, before the first boats were made. The sight of a crow standing on a piece of driftwood floating down the swollen current of a creek or river, might well enough suggest the specific idea to a savage, that he could himself get upon a log, or on two logs tied together, and somehow work his way to the opposite shore of the same stream. Such a suggestion, so taken, would be the birth of navigation; and such, not improbably, it really was. The leading idea was thus caught; and whatever came afterwards, were but improvements upon, and auxiliaries to, it. As man is a land animal, it might be expected he would learn to travel by land somewhat earlier than he would by water. Still the crossing of streams, somewhat too deep for wading, would be an early necessity with him. If we pass by the Ark, which may be regarded as belonging rather to the _miraculous_ than to _human_ invention, the first notice we have of water-craft is the mention of “ships” by Jacob (Genesis xlix: 13). It is not till we reach the book of Isaiah that we meet with the mention of “oars” and “sails.” As man’s _food_--his first necessity--was to be derived from the vegetation of the earth, it was natural that his first care should be directed to the assistance of that vegetation. And accordingly we find that, even before the fall, the man was put into the garden of Eden “to dress it, and to keep it.” And when afterwards, in consequence of the first transgression, _labor_ was imposed on the race, as a _penalty_--a _curse_--we find the first born man--the first heir of the curse--was “a tiller of the ground.” This was the beginning of agriculture; and although, both in point of time, and of importance, it stands at the head of all branches of human industry, it has derived less direct advantage from Discovery and Invention, than almost any other. The plow, of very early origin; and reaping, and threshing, machines, of modern invention are, at this day, the principal improvements in agriculture. And even the oldest of these, the plow, could not have been conceived of, until a precedent conception had been caught, and put into practice--I mean the conception, or idea, of substituting other forces in nature, for man’s own muscular power. These other forces, as now used, are principally, the _strength_ of animals, and the _power_ of the wind, of running streams, and of steam.