254 WRITINGS OF JOSEPH HENRY. [1846 



dition of the atmosphere by equalizing the quantity of the 

 fluid in different places, and thus producing a less change- 

 able state of the weather. The feeble currents of electricity 

 which must be constantly passing along the wires of a long 

 line may however, with proper study, be the means of dis- 

 covering many interesting facts relative to the electrical 

 state of the air over diflFerent regions.* 



ON THE "fountain-ball," AND ON THE INTERFERENCE OF 



HEAT. 



(Proceedings of the American Philosophical Society, vol. iv, p. 285.) 



Octoier 16, 1846. 



Professor Henry laid before the Society the results of some 

 investigations that he had lately made on two questions in 

 physical science, and a theory of the causes of the phenomena 

 observed. 



The well known phenomenon of a ball resting on a jet of 

 water he ascribed to the action of three different causes: 

 1st, to the adhesion of the water to the ball: 2d, to the 

 adhesion of the water to itself: 3d, to the tendency of water 

 to move in a straight line and also to the principle of action 

 and re-action. 



He had also made experiments in regard to the interfer- 

 ence of heat for the purpose of discovering whether certain 

 phenomena of interference of light were exhibited as well in 

 the case of heat. He found it to be so, and that two rays of 

 heat may be thrown on each other so as to produce a reduc- 

 tion of temperature. 



* [Re-printed in Silliman's American Journal of Science, 1847, vol. in, 

 pp. 25-32. Also in the London and Edinburgh Pliilosophical Magazine, 

 1847, vol. XXX, pp. 18G-194.] 



