FllBRUAKY 7, 1896.] 



SCIENGE. 



195 



he found everywhere a large and apprecia- 

 tive constituency, while his own almost 

 boyish pleasure in whatever he saw that was 

 novel was charming to see. On his home- 

 ward voyage he met with an accident which 

 was thought by many to be the beginning of 

 the end. Up to the time of his death, which 

 occurred about a year later, he continued, 

 but not very actively, to direct the great in- 

 stitution for original research, in which, by 

 the wisdom of an appreciative government, 

 he had found full scope for his powers. His 

 interest in the important work done at the 

 Chicago Congress continued through this 

 year, and one of the few long letters he 

 wrote had reference to its proceedings. On 

 the 8th of September, 1894, he died, and on 

 the 13th he was buried at Charlottenberg, 

 princes and peasants alike mourning his 

 loss. 



Von Helmholtz occupied so large a part 

 of the scientific horizon and for so long a 

 time that we have not yet become accus- 

 tomed to his absence. But it is not too 

 soon to agree that the following admirable 

 lines which appeared in the London Punch a 

 little more than a year ago express in some 

 measure our judgment of the man and his 

 work: 



' ' What matter titles ? Helmholtz is a name 

 That challenges alone the award of fame! 

 When Emperors, Kings, Pretenders, shadows all. 

 Leave not a dust- trace on our whirling ball, 

 Thy work, oh grave-eyed searcher, shall endure, 

 Unmarred by faction, from low passion pure." 



T. C. Mendenhall. 



CURRENT NOTES ON PHYSIOGRAPHY. 

 THE TEMPERATURE OF LAKES. 



A CAREFUL study of the temperature of 

 lakes, leading to important economic results 

 in connection with water supply, has lately 

 been completed by Desmond Fitzgerald, of 

 the Boston Water Works (Trans. Amer. 

 Soc. Civil Engineers, xxxiv, 1895, 67-109). 

 Many of the observations have been taken 



with the thermophone (see Amer. Meteorol. 

 Journ., xii, 1895, 35-50), thus gaining much 

 accuracy and saving much time. It appears 

 from the numerous diagrams and tables in 

 the essay, as well as from the text, that 

 small water bodies, such as Lake Cochit- 

 uate, one of the chief supplies for Boston, 

 are generally in stable equilibrium. During 

 the winter, when small lakes are frozen, 

 the surface water to a depth of about ten 

 feet is colder and lighter than the great 

 body of deeper water whose temperature is 

 that of maximum density. All through 

 the summer, stability and stagnation again 

 prevail, the surface water to a depth of 

 thirty or forty feet being then warmer and 

 Ughter than the bottom water, which re- 

 mains between 40° and 45°. During this 

 summer period of stagnation, and after the 

 oxygen dissolved in the water has been used 

 in the decomposition of sinking organic 

 substances, they accumulate for the re- 

 mainder of the season; the water then be- 

 comes darker and darker, until by October 

 it is very yellow and generally of a disa- 

 greeable smell. But in April, and again in 

 November, the temperature of the lake is 

 essentially constant from top to bottom ; 

 the water body is then in indifferent equili- 

 brium and is easily overturned by the 

 wind. In ^November particularly this over- 

 turning brings all the impure bottom water 

 to the surface; infusoria and diatoms begin 

 to grow in enormous numbers, because of 

 the supply of food thus provided. While 

 the degree of impurity of the stagnant bot- 

 tom water varies in different lakes, it may 

 in some become a serious annoyance ; and ' 

 it is suggested that, where possible, the 

 bottom water should there be drawn off 

 from reservoirs and ' wasted ' before the 

 November overturning arrives. 



WINDS INJURIOUS TO VEGETATION AND CROPS. 



Under the above title, the late Prof. Greo. 

 E. Curtis contributed to the International 



