SECRETARY'S REPORT. 149 



come together, refraction is inevitable. Under the influence of 

 refraction the heat of the sun is turned out of its course. Tlic 

 heat of the sun comes from empty space into an atmosphere 

 which increases in density from the surface toward the earth, 

 and is refracted as light is refracted when passing from the air 

 into water ; which is familiar to all. 



The question is, how is this heat of the sun refracted ? It is 

 refracted in such a way as to be concentrated upon certain lati- 

 tudes and longitudes, having a kind of concentration of rays in 

 some particular place, as the burning-glass concentrates heat to 

 a focus. I do not say that there is an actual focus produced by 

 the atmosphere, though there evidently must be one somewhere. 

 However that may be, the heat is concentrated upon certain 

 latitudes and longitudes by passing through the atmosphere thus 

 elevated in a convex form. There must consequently be, a with- 

 drawing of heat from other portions of the earth, and the 

 production of cold, which is merely the absence of heat. This 

 is the reason why it is often much colder in latitudes south of 

 us, at a given time, than it is here ; and also colder in one place 

 than in another in the same latitude. There is a uniform corre- 

 spondence between these facts, as they occur, and other facts 

 connected with the position of the sun and moon ; and they are 

 all to be explained upon the philosophical principles to which I 

 have called your attention. 



When the moon culminates at twelve o'clock, M., the condi- 

 tion of things is favorable for the action of the sun, for it rises 

 on the full tide. In the latitude of Boston there are seldom 

 storms when the moon comes to the meridian between six 

 o'clock and twelve. Sometimes there will be storms when the 

 moon culminates at seven, nine or eleven. This science has 

 been reduced to so great accuracy, that we can calculate within 

 less than two minutes those periods of time, between six in the 

 morning and twelve, when the focal crises will occur ; that is, 

 when there will be periods in which the thermometer will rise, 

 and in which, a few moments after, a chill will occur. These 

 principles were illustrated at length. 



Mr. Capen closed by a statement of the causes that led him to 

 a study of this subject, and which produced in his mind an 

 unfaltering belief in its importance. 



