64 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



salmon into any given stream will depend upon the relation- 

 ship of its temperature during the summer and autumn to 

 the particular species ; some kinds, as the true salmon of the 

 North Atlantic {Salmo salar)^ requiring a summer minimum 

 of at least sixty to sixty-five degrees, while others will bear a 

 higher temperature. 



SIGNAL-OFFICE KIVER KEPOETS. 



The army Signal-office has made preparations for a very 

 great extension of its valuable system of reports of the 

 heights of rivers, particularly of all those opening into the 

 Mississippi. Over twenty-five stations are now established 

 at suitable points on these rivers, especially, of course, on the 

 Ohio, Missouri, and Mississippi. They are provided in some 

 instances with automatic self-recording apparatus, and at all 

 other places the observation of the height of the water is 

 taken eight times daily wdien floods are apprehended. By 

 this most beautiful system every wave of high water is accu- 

 rately followed in its course down stream, and the approach 

 of dangerous high floods is easily foretold by the repeated 

 telegraphic reports. The system of river reports, which has 

 been in operation during the past year, has given such uni- 

 versal satisfaction to those navigating the Western waters 

 that the demand for increased facilities can only be met by 

 this new and far more elaborate system of stations. 



The universal interest and value of the systematic tele- 

 graphic reports of the weather and of the rivers now fur- 

 nished by the army Weather Bureau show what a power the 

 electric telegraph is destined to become when its ramifica- 

 tions shall be still further extended, and the expense of using 

 it cheapened. 



CRUISE OF THE NEW YORK SCHOOL-SHIP MERCURY. 



The New York Nautical School-ship Mercury has spent the 

 past winter in deep-sea research, as in a previous season, and, 

 as before, has utilized the opportunities presented in the in- 

 terest of science. Captain Giraud addresses the president of 

 the board of Commissioners of Public Charities and Correc- 

 tion from Rio, under date of January 25, stating some of the 

 points in which he regarded his operations as successful in 

 connection with deep-sea soundings and temperatures. He 



