1405. The variable winds cannot be so readily accounted for; yet it is evident that, though they seem the effects of capricious causes, they depend upon a regular system, arranged by the great Author of nature. That accurate and successful observer of part of his works, the celebrated Franklin, discovered, in 1740, that winds originate at the precise points towards which they blow. This philosopher had hoped to observe an eclipse of the moon at Philadelphia, but was prevented by a north-east storm, that commenced at seven in the evening. This he afterwards found did not occur at Boston till eleven; and, upon inquiry, he had reason to suppose it passed to the north-east at the rate of about 100 miles an hour. The manner in which he accounts for this retrograde proceeding is so satisfactory, that we shall give it in his own words, particularly as his assertions are supported by recent observations, both in America and Scotland. He argued thus:-'I suppose a long canal of water, stopped at the end by a gate. The water is at rest till the gate is opened; then it begins to move out through the gate, and the water next the gate is put in motion and moves on towards the gate; and so on successively, till the water at the head of the canal is in motion, which it is last of all. In this case all the water moves indeed towards the gate; but the successive times of beginning the motion are in the contrary way, viz. from the gate back to the head of the canal. Thus, to produce a north-east storm, I suppose some great rarefaction of the air in or near the Gulf of Mexico; the air rising thence has its place supplied by the next more northern, cooler, and therefore denser and heavier air; a successive current is formed, to which our coast and inland mountains give a north-cast direction.' According to the observations made by Captain Cook, the north-east winds prevail in the Northern Pacific Ocean during the same spring months they do with us, from which facts it appears the cold air from America and the north of Europe flows at that season into the Pacific and Atlantic Oceans.
