140 ROCHESTER ACADEMY OF SCIENCE. [May 9, 



The theory has been advocated that these re-arrangements of 

 pressure and coincident peculiarities depend upon accidental terres- 

 trial conditions. It has been said for example, that drift ice in the 

 North Atlantic would produce unusual cold over the adjacent conti- 

 nents. That this is not so appears from what has just been stated in 

 the preceding paragraph. It is precisely when the winters are mild- 

 est over the northern parts of Europe and America that such ice is 

 most abundant. 



It has been customary also to ascribe such wholesale re-arrange- 

 ments in weather conditions to variations in the sun's power of heat 

 emission. This has been done upon purely theoretical grounds, no 

 direct evidence of any such variation having been secured by the 

 exposure of properly arranged thermometers to the direct rays of the 

 sun in the most favorable localities that can be found. Furthermore, 

 when the averages from a sufficiently large number of stations are 

 compared, it is found that the excesses and deficiencies offset each 

 other in such a manner that the general result is but an insignificant 

 departure from the normal. In other wordS; there are re-arrangements 

 of distribution but the quantity remains the same. From the point 

 of view of the present discussion the question as to the variability of 

 solar heat resolves itself into an inquiry as to whether the inductive 

 forces emanating from the sun under the limitations that have been 

 pointed out are of a thermo-electric nature. 



The periodicity corresponding to the time of a synodic revolu- 

 tion and the confinement of magnetic effect to a very small portion of 

 each transit, which portion remains the same at successive returns, indi- 

 cate that the motion of rotation and not heat radiation is concerned in 

 the propagation earthward of these impulses. Rays of heat pass 

 indifferently in every direction through a homogeneous medium such 

 as is that surrounding the sun. Hence there is no possibility of 

 accounting for the eastern limb effect by the agency of heat rays 

 inasmuch as this would necessitate their emission in a single direction 



■only. The same is true of light radiations. Whatever may be the 

 merit of the electro-magnetic theory of light it does not apply in this 



•case. In other words the magnetic effect of solar disturbances does 

 not depend upon their visibility. If this were the case magnetic 



•storms and auroras would continue all the while in certain years, 

 whereas even when the sun is most disturbed continuance for as long 



•a time as a single week is extremely rare. 



It is the motion of rotation of portions of the sun's surface that 



(have been electrified by the action of eruptive forces that developes 



