Eacll-v'pctical interspace represents one decree Fahrenheit, and tlie fracdonai parts of a degree are indicated as exacdy as possible in the plotting of die curves. Eacli fifth 

 degree is represented by a slightly heavier, line. The transverse' interspaces inclosed by the heavier lines represent periods of ten days each, as indicated by the daces on the 

 lefehandsfde of the plate. The lighter transverse lines, intermediate between the heavier. ones,' are intended to represent die mean of each ten days, and the curves of temper- 

 atuxEareplottedwidireference to 'these lines. The left-hand vertical division. is devoted to the air temperatures for' 1 88 1, i8S 2 and 18S3, die middle division to die surface 

 water temperatures for^the same years, thus permitring of a comparison of die'two; and the ri;,'ht-hand division to die water temperatures for 1S84 and 1885. 



