380 



On the Heat in the Sun's Rays. 



No. of obs. 



Temp, of air. 



Temp, in sun. 



Diff. 



xvciauvci Ileal, \Jl 



sun's rays. 



1 



- 40 



46 



6 



6 



2 



44 



50 



6 



10 



3 



48 



56 



8 



16 



4 



50 



60 



10 



20 



5 



54 



66 



12 



26 



6 



58 



70 



12 



30 



7 



63 



80 



17 



40 



8 



70 



90 



20 



50 



9 



78 



100 



22 



60 



10 



83 



106 



23 



66 



11 



88 



110 



22 



70 



12 



98 



120 



22 



80 



13 



102 



124 



22 



84 



14 



108 



130 



22 



90 



1st. That the heat in the sun's rajs is not uniform, such as 

 would proceed .from a great heated body of uniform intensity, 

 nor is it such as was received from the canister, when kept at the 

 same degree of heat, but that it varies and is dependent upon 

 the temperature of the air. 



2ndly. That the effects of the sun's rays upon the thermometer 

 at the different degrees of heat in the receiver is the same that 

 has usually been observed at similar temperatures in the open 

 air. It is easy by changing the heat within the receiver, to imi- 

 tate the power of the sun's rays that has been observed at any 

 time or in any place ; indeed at the same time, the same rays may 

 have in one receiver the burning heat of a summer's sun, and in 

 the other only the feeble action of winter. 



3dly. It appears that heat does not travel along with the rays 

 of light as has been usually supposed, but that it is received, or 

 parted with, lost or acquired, according to the temperature of the 

 place that the rays illuminate. The same rays that within the 

 receiver have the high intensity belonging to summer, on passing 

 to the outside, are reduced again to a winter's temperature. . 



In view of these results it seems to me to accord better with 

 the facts to attribute to the sun's rays, perhaps to all light, an 

 action of some kind on such heat as they come in contact with, 

 producing thereby the effects that we have been accustomed to 

 attribute to an enormous temperature in the sun. Each planet 

 may be supposed to possess its own atmosphere of heat : this will 

 be affected by the sun's light as the heat within the receiver 

 was affected ; but they need not be frozen by their great dis- 

 tance, nor burned by their near approach to the great luminary. 



It becomes an interesting and important enquiry, to ascertain 

 the circumstances that affect the action of light on heat. 



One of the most obvious is, that the amount of action de- 

 pends upon the quantity of light. The clearness of the atmos- 

 phere always affects the experiment, making it somewhat diffi- 

 cult to compare observations taken at different times. A strong 

 light obtained by reflection or otherwise, always increased the 



