Page:McCosh, John - Advice to Officers in India (1856).djvu/326

 feel assured that it is quite practicable to pass through the surf without inconvenience,and to load and unload cargo without damage or danger even by our own ships' longboats.

"The theory of the surf is, I believe, simply this:—As the wave rolls landward, the lowest stratum of water is retarded by friction against the bottom; while the upper stratum not so retarded outstrips the lower stratum, topples over and breaks into a surf, high in proportion to the height of its parent wave. This law of fluids is still better observed in air than in water. In a dust cloud drifting along the road, or a rain cloud along the horizon, the upper stratum is always in advance of the lower;and in the dust storms that prevail in the Punjaub, converting the light of noon into the darkness of midnight, the whole hemisphere is obscured long before the hurricane is felt below, the velocity of the wind being retarded by the resistance on the surface of the earth."

If we could throw the same obstruction continuously on the surface of the water,that it meets with on the bottom, no Surf could take place, and the wave, as it rolled on, would gradually subside, and reach the sand in a mere ripple.

"I can quote facts from personal experience in support of this theory. On the great river Megna, far from the protection of land,I have rode out a