Each vertical interspace represents one degree Fahrenheit, and the 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 interspaces inclosed by the heavier lines represent periods of ten days each, as indicated by the dates on tlie 

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

 ature are plotted with reference to these lines. The left-hand vertical division is devoted to the air temperatures for iSSi, 1882 and 1883, the middle division to tlie surface 

 wafer temperatures for the same years, thus permitring of a comparison of the two; and the right-hand division to die water temperatures fof 1884 and iSSs. 



