The history of a raindrop, then, has some very romantic and interesting episodes connected with it; but, wonderful as are the incidents in what is really a very remarkable career, it is not until the raindrops fall on the earth that the full purport of the work they do is wholly realized. Contemplated by itself, a raindrop seems a very insignificant thing; but when the drops combine in a heavy downpour of rain the result is truly wonderful. The information that one inch of rain has fallen over a certain area is not very impressive; the amount does not seem very great. A fall of one inch of rain means, however, that no less than one hundred tons of water have fallen on each acre of surface, or no less than sixty thousand tons on each square mile. Instead of expressing the amount of water in tons, it may be thus stated in gallons, taking the Thames basin as a convenient area for reference: a rainfall of three inches over that area means that one hundred and sixty thousand million gallons of water have been precipitated from the atmosphere. At times, too, when the rainfall is still heavier, rivers overflow their banks and floods occur, and still further evidence is then forthcoming of the power and the might of the raindrops working toward one common end. Sooner or later the raindrop, whether it runs off the surface of the earth in a river or in a disastrous flood, finds its way, under the influence of evaporation, back into the atmosphere, and is then ready to start on another journey, which, like all its predecessors, will be full of incident from start to finish. THE RAINBOW --JOHN TYNDALL The oldest historic reference to the rainbow is known to all: “I do set my bow in the clouds, and it shall be for a token of a covenant between me and the earth.... And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the earth.”