134 NOMOS. 



of the earth is no evidence that the ray-currents of 

 the sun do not penetrate beyond this depth, but, on 

 the contrary, it only shows that up to this point 

 these rays encounter certain obstacles to their free 

 transmission. According to the premises, indeed, 

 the fluctuating heat of the superficial strata is only 

 the sign of certain overplus ray-currents which can- 

 not be transmitted in consequence of the deficient 

 conducting powers of the earth. 



Nor does it follow from these facts that the heat is 

 transmitted slowly through the earth. On the con- 

 trary, the views which make heat the sign 

 heat may tra- of the current give heat the velocity of the 

 current, and this velocity is to be measured, 

 if measured at all > by the rapidity with 

 which the message flies along the tele- 

 graphic wire. Nay, it does not follow that the evi- 

 dences of heat are transmitted through the superficial 

 strata as slowly as is supposed, for it may be that 

 the more active ray-currents of summer are better 

 able to travel through these superficial strata than 

 the weaker ray-currents of winter, and that, for this 

 reason, there may be less opposition in the strata, 

 and consequently less " heat given out," in July, 

 when the currents are strongest, than in January, 

 when they are weakest. All this is possible, and if 

 so then the fall of the thermometer will simply show 

 that the ray-currents are transmitted more readily 

 than when the thermometer stood at a higher point ; 



and vice versa. 



* By thus regarding the phenomenon of heat, it is possible, in 

 some degree, to comprehend the causes of lenticular action. It is 



