EXPLANATION OP OCEAN TEMPERATURE CHART No. 30. 



Isotbermal lines connecting the series of light-house stations on the eastern coast of the United States, represented 

 on Chart No. 1, constructed for every 5° of temperature, Fahrenheit, from 40° to 80°, inclusive, for the year 1885. 



At the time this chart was prepared, the temperature records for 1886 were not available, and it was, therefore, 

 impossible to plot the isotherm of 40° during the period of falUug temperature, excepting for those stations at which 

 that temperature was reached in December. As iu most previous years, higher temperatures than 55° were recorded 

 at Petit Manan, although the isotherms of 55° extended north continuously only as far as Segnin Island. 



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