Page:Popular Science Monthly Volume 41.djvu/442

428 the temperature of the water. Under conditions appearing to be the same, and at points relatively near to each other, the water on the surface of the lakes and rivers is not uniform in temperature, but seems to flow in areas of different temperatures. It is impossible to lay down any general rule regarding the changes of temperature varying with the increase in depth. Apart from variations resulting at the different seasons, surface readings are affected by sunlight and cloud, gusts of wind, channel currents, the inflow of affluent streams, and the physical features of the surrounding land. Readings beneath the surface are affected by the depth of the water, by ordinary currents resulting from changes of level, by evaporation at the surface creating an upward flow of the water underneath, by the contour of the bottom, and by high winds which drive the surface waters before them, creating return currents underneath to take their place. The general rise of the temperature of Lake Ontario waters as the summer advances is at first slow, compared with the general rise of the temperature of the air, but, as midsummer is reached, the rise is more rapid both at the surface and at the bottom. The absorption and retention power of the sun's heat is most noticeable in the small streams and quiet pools. In the case of rivers, the air in direct contact with the warm surface of the water has its temperature in early August raised to from 1° to 5° above that of the air directly above, but in more exposed positions; and this increase in temperature, which is greatest at the point of contact, is, at one foot above the surface of the water, already to a considerable extent lost.

The Value of Human Testimony.—The argument of a book by Mr. Thomas Fitzarthur on the Value of Human Testimony is, according to the summary of The Spectator, that the value depends in a great measure on the importance attached by the witness to the facts to which he testifies. If the fact is insignificant, if his interest in it is languid, and it has no real bearing on his life, it is not to be supposed that he will take the trouble to attend to the matter with the care and the anxiety to be sure of what he sees or hears which is necessary to make his testimony of real weight for other people. But if it is a fact on which a great change in his own career depends, if it alters his whole life, his whole character, if it involves him in much labor and suffering, if it kindles in him an altogether new ideal of purpose, then we may be sure that his testimony is both honest and careful, and that, if it is supported by a great deal of other testimony of the same nature, it is in the highest degree trustworthy. Further, the author insists that its transmission through a long line of tradition does not invalidate its authority. We should not attach much value to details so transmitted. If we were dependent on testimony transmitted from generation to generation as to the numbers and character of the forces engaged in the battle of Hastings, we should not attach much weight to it. But such a long line of transmission would not diminish the value of the testimony as to the reality of that battle, and its result in the defeat of the Saxon and the victory of the Norman army. We should be well aware that that testimony must have been transmitted through a great many unwilling as well as a great many willing and triumphant witnesses. We should be well aware that all those witnesses must have had before their eyes the amplest evidence of the actual event, and of the revolution it brought about in the history of England. And we should never think of supposing anything so absurd as that at some specific date there was a deliberate conspiracy formed by hundreds of thousands of living Englishmen to alter the whole drift of the testimony they had received from their fathers, and invent a battle which never took place, or reverse its issue, and that that conspiracy should have succeeded in persuading the unborn generations to believe a gigantic lie. There could be neither machinery nor motive for such a successful conspiracy, and consequently the common sense of mankind at once rejects a hypothesis so audacious and absurd, with contempt.

Miss North's Animal Friends.—Miss Marianne North relates, in her Recollections, that while sketching an old Hindu temple at Blaune Watu, Java, she felt hungry and began eating a biscuit as she went on with her work. Shortly she was disturbed by a pull at her dress, and found a large monkey sitting beside her and looking reproachfully at