Each -vertical interspace represents one degree Fahrenheit, and tlie fractional parts of a degree are indicated as exactly as possible in the plotting of the curves. Each fifth 

 degree is represented by a slighdy heavier line. The transverse inierspaces inclosed by the heavier lines represent periods of ten days each, as indicated by the dates on the 

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

 ature are plotted widi reference to these lines. The left-hand vertical division is devoted to the air temperatures for iSSi, 18S2 and 1803. the middle division to the surface 

 ■water temperatures for the same years, thus permitting of a comparison of the two; and the ri^htJiand divisioa to the -water, temgeratures for 18S4. and 1SS5. 



