428 



THE POPULAR SCIENCE MONTHLY. 



izing 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 impos- 

 sible to lay down any general rule regarding 

 the changes of temperature varying with the 

 increase in depth. Apart from variations re- 

 sulting at the different seasons, surface read- 

 ings are affected by sunlight and cloud, gusts 

 of wind, channel currents, the inflow of afflu- 

 ent streams, and the physical features of the 

 surrounding land. Readings beneath the sur- 

 face are affected by the depth of the water, 

 by ordinary currents resulting from changes 

 of level, by evaporation at the surface creat- 

 ing 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 tem- 

 perature 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 Valne of Human Testimony. The 



argument of a book by Mr. Thomas Fitzar- 

 thur on the Value of Human Testimony is, 

 according to the summary of The Spectator, 

 that the value depends in a great measui'e 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 ca- 

 reer 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. Fur- 

 ther, the author insists that its transmission 

 through a long line of tradition does not in- 

 validate 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 num- 

 bers 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 un- 

 willing 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 re- 

 ceived from their fathers, and invent a bat- 

 tle which never took place, or reverse its 

 issue, and that that conspiracy should have 

 succeeded in persuading the unborn genera- 

 tions 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 con- 

 tempt. 



Miss North's Animal Friends. Miss Ma- 

 rianne North relates, in her Recollections, that 

 while sketching an old Hindu temple at 

 Blaune Watu, Java, she felt hungry and be- 

 gan 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 sit- 

 ting beside her and looking reproachfully at 



