One of the hallucinations entertained by nearly every adult person is that the climate has changed since he was young. No matter what the scientists may say, he knows that it has changed. Fifty years ago did he not trudge to school for months every winter in snow knee-deep? Have not the old swimming holes in the brook dried up? Yes, he is a positive witness to an affirmative answer. Even the river of his boyhood, whose broad expanse he conquered in a swimming contest at the tender age of ten—as he views it after an absence of a quarter-century—has dwindled to little more than a creek, across which one easily may hurl a stone. Talk to him about no change in climate. He’s been right on the spot, and knows. For all this, there has been no change during the lifetime of this man; nor has there ever been during the life period of any individual. Mutations, to be sure, are going on all the time, but they are so minute that they do not accumulate a measurable quantity except in periods of hundreds or thousands of years. It is not the climate that has changed; it is the man. The natural action of the stream may have filled the swimming holes; or the stream may have entirely disappeared through much of the contiguous area being brought under cultivation and the water that formerly supplied its flow being utilized in the production of cultivated crops, which actually make use of as much if not more rainfall than the forest that formerly lined its sinuous banks and covered the near-by lowland. And then, snow knee-deep to a boy of ten hardly comes up to the ankles of a man of six feet two. Again, no one can remember the climate of his boyhood; he cannot carry the average in his mind; all that he can remember are a few instances of unusual conditions which because of their unusual character left an impress upon his mind. The river is just as wide as it ever was during the period of his lifetime, or that of his father, or of his grandfather; but he has lived on the broad Mississippi for many years, and when he goes back to the scenes of his youth, his concept of what constitutes a river has undergone a revolutionary change since he left the parental roof to go forth and conquer the world. An examination of the personal papers of Thomas Jefferson, in the State Department at Washington, by an official of the Weather Bureau, revealed a number of most interesting incidents in connection with the weather observations made by the author of the Declaration of American Independence. He says: