224 WKITINGS OF JOSEPH HENRY. [1845 



ON A PECULIAR ACTION OP FIRE ON IRON NAILS. 



(Proceedings of the American Philosophical Society, vol. iv, p. 173.) 



June 20, 1845. 



[Dr Patterson exhibited a mass of nails melted together at 

 the fire in Pittsburg, presenting a series of united tubes.] 



Professor Henry stated that he had received a similar mass 

 from the New York fire, and found that the action of the fire 

 had changed the nails to a certain depth, leaving a core un- 

 changed, which had afterwards fallen or been drawn out, 

 leaving the hollow tube. 



OBSERVATIONS ON THE RELATIVE RADIATION OF THE SOLAR 



SPOTS. 

 (Proceedings of the American Philosophical Society, vol. iv, pp. 173-176.) 



June 20, 1845. 



Professor Henry made a verbal communication of a series 

 of experiments made by himself and Professor Alexander, 

 relative to the spots on the sun. 



His attention was directed to the subject by an article in 

 the September number of the Annales de Chimie, by M. 

 Gautier, upon the influence of the spots on the sun on terres- 

 trial temperature. It is well known that Sir William 

 Herschel entertained the idea that the appearance of solar 

 spots was connected with a more copious emission of heat, 

 and that the seasons during which they were most abundant 

 were most fruitful in vegetable productions, and pursuing 

 this idea he was led to trace an analogy between the price 

 of corn and the number of solar spots during several succes- 

 sive periods. The result of this investigation, so far as it was 

 extended, seemed to favor the views of this distinguished 

 philosopher. A mode of investigation of this kind however 

 is not susceptible of any great degree of accuracy ; the price 

 of corn is subject to so many other causes of variation besides 

 that of solar temperature that little reliance can be placed 

 on this condition alone. 



