£ach 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 

 ! is reptesented by a slighdy heavier line. The transverse Interspaces inclosed by the heavier lines represent periods of ten days each as inaicate.d by the dates on the' 

 left-hand Sde of the plate. The lighter transverse lines, intermediate between itlie 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 ^emperatures for i8Sf, 1882 and l8S3,the middle divisioa to the suifacB 

 waterJtejnperatJires for die same yeacsj thus permitring of acpmparisonof «the two; and die right-iiand division toihe water temperatures for 1884 and 1885. 



