1867.] 309 [Chase. 



Mr. P. E. Chase made an oral communication on the laws 

 which regulate the transmission and distribution of solar heat. 



Prof. Dove, in the discussions by which he demonstrated the ex- 

 istence of consistent and clearly-marked annual barometric tides, 

 has well set forth the importance of broad meteorological generaliza- 

 tions. It is, evidently, only by a comparison of observations made 

 in all quarters of the globe, that we can hope to find the funda- 

 mental laws which regulate periodical changes in the atmosphere, 

 and thus become properly qualified for the study of local and ex- 

 ceptional disturbances. 



It seems somewhat remarkable, that, in a science so eminently 

 statistical as meteorology, the formidable mass of already accumu- 

 lated observations has been followed by such raeagreness of practical 

 results. Humboldt and Dove have admirably developed the system of 

 isothermal lines, the latter having widely tracked it through its theral, 

 chimenal, monthly, and annual ramifications; but these lines are so 

 largely controlled by ocean currents, mountain ridges, and other 

 local disturbances, that they give us little help towards ascertaining 

 the laws which regulate the distribution of heat over the earth's sur- 

 face. Mayer believed that the normal mean temperature varies as 

 the square of the cosine of latitude. The error of his formula was 

 soon demonstrated, and I am not aware that any one has proposed a 

 substitute. The active members of the various meteorological so- 

 cieties are industriously engaged in the solution of numerous special 

 problems, and the indefatigable host of observers are evermore add- 

 ing to the stores of material, but the laborers are too few for the 

 harvest. We are still entirely ignorant of the degrees of influence 

 exerted by the various well-known climatic causes in determining 

 the mean temperature of the several seasons and of the entire year. 



The principal elements of general thermometric variation are: 1, 

 the heat imparted by the sun ; 2, terrestrial absorption and radiation; 

 3, atmospheric currents. Of these three agencies, the first is, in 

 one sense at least, the chief, since it is the one on which the others 

 depend; the second is mainly instrumental in modifying the other 

 two, and especially' in retarding the daily and yearly changes ; the 

 third is a subject of hourly experience, and its meteorological im- 

 portance is now generally recognized. 



The amount of heat which is received directly from the sun, evi- 

 dently varies as the cosine of the zenith distance, or the sine of the 



