SCIENCE. 



FRIDAY, APRIL 9, 18t?6. 



COMMENT AND CRITICISM. 

 The rise and fall of the waters in the north- 

 western lakes, and the consequent dangers to the 

 lake cities, have frequently been a sensational sub- 

 ject for discussion. The great tidal waves, like 

 the one which rolled in on Cleveland a few years 

 since, and the piling-up or lowering of the waters 

 by continued gales, are, of course, real dangers on 

 account of the suddenness of their occurrence, 

 though, happily, they are rare and temporary 

 events. But alarmists are continually announ- 

 cing the discovery that the gradual or secular 

 changes in the lake-levels are sure to bring dis- 

 astrous results. According as the waters are 

 rising or falling, we hear of grave fears that some 

 lake-post is likely to be inundated, or left high and 

 dry inland. Recent reports in the daily press in- 

 dicate that Lake Michigan is assuming a tlueaten- 

 ing attitude towards Chicago and its suburbs. 

 The lake is now rising, the reports state, at the 

 rate of several inches per year ; and one needs 

 only to imagine this rise prolonged at the ob- 

 served rate for a few years to get an idea of star- 

 tling possibilities for the Garden city. But the 

 records of the fluctuations in water-level of the 

 Great Lakes, which have been carefully kept for 

 many years by the corps of engineers, U.S.A., do 

 not warrant us in prolonging any observable rise 

 or fall indefinitely. On the contrary, these records 

 indicate that the variations in the lake-levels, 

 above or below the mean stage, are confined to 

 a very few feet, — about three feet at the most. 

 The variations are greatest in Lake Ontario, less 

 in Lake Erie, still less in Lakes Huron and Michi- 

 gan, which form a single level surface, and least 

 of all in Lake Superior. With reference to Lake 

 Michigan in particular, a glance at the water-level 

 curves published in the report of the chief of engi- 

 neers, U.S.A., 1882 (the curves do not appear to 

 be published in the later reports), shows that the 

 average yearly variation in level of that lake is 

 about one foot, that the maximum variation dur- 

 ing any one year included in the period (1859-82) 

 covered by the published record was two feet and 

 a half, and that the extreme fluctuation during 



No. 166. — 1886. 



the same period from the highest stage (in 1859 or 

 1876) to the lowest stage (in 1869 or 1873) was three 

 feet and seven-tenths. The highest recorded stage 

 of Lake Michigan, viz., that of 1838, was only one 

 foot higher than the stage of 1859 or 1876. It 

 seems tolerably safe, therefore, to conclude that 

 the prospective dangers to Chicago or any of the 

 lake cities from too much or too little water in the 

 lakes are all such as may be overcome by acts of 

 congress in the shape of timely items in the river 

 and harbor bill. 



The outline - map of the United States in four 

 sections, prepared by Dr. A. B. Hart of Harvard, 

 and lately issued by D. C. Heath & Co., may be 

 a means of leading the numerous teachers of his- 

 tory throughout the country to adopt more scien- 

 tific methods of instruction. On this account 

 alone, and wholly apart from its intrinsic excel- 

 lence, it deserves recognition and notice. The 

 map is in four sections, each thirty-one by forty- 

 four inches, the United States being divided at the 

 37th parallel and at the 95th meridian. Being in 

 outline, and showing the principal w r ater-courses, 

 a skilful teacher can, without any great ability as 

 a draughtsman, color the map so as to present in 

 graphic form geological facts or the course of 

 political and social development. Changes of popu- 

 lation, the local strength of political parties, the 

 distribution of railways, schools, or industrial 

 establishments, topographical features, — in short, 

 any thing which admits of statistical and graphic 

 presentation, — can be shown with a minimum of 

 expense and labor. The map is so cheap that a 

 teacher can easily procure a number of them ; 

 and, w r hen once colored to illustrate any particular 

 subject, they can be rolled up, and used again at 

 any future time. 



We would suggest that the principle here ap- 

 plied by Dr. Hart to United States geography and 

 history will bear extension. The map should be 

 reproduced on a smaller scale for the use of 

 pupils ; for, by copying the display-map on an 

 outline of his own, the facts will be more deeply 

 impressed upon the student's mind, and he will 

 always have a graphic summary of them for 

 reference. We shall soon hope to see outline- 



