OPTICAL EFFECTS OF INTENSE HE A T AND LIGHT. 317 



walls, except those that shield guns ; for service and storage magazines ; for 

 pavements of magazines, casemates, galleries, etc., and generally for all masonry 

 not exposed to the direct impact of an enemy's shot and shell." 



OPTICAL EFFECTS OF INTENSE HEAT AND LIGHT. 



BY JOSHUA THORNE, M. D. 



The following facts have lately come under my observation at the rolling 

 mills at this place : 



While looking at the eclipse of the sun July 29th, I handed the glass to one 

 of the mill " heaters." He at once told me he could see as well with the naked 

 eye as with the smoked glass. I then tried another "heater," and he at once re- 

 peated the same statement. I then went to the rolling mill and tested every 

 "heater" at his furnace. They all told the same story. I hunted up every 

 "heater" in the town except two (who were not found), over twenty in all, and 

 everyone declared he could see the phenomenon, and all its phases, as well or 

 better with the eye unshaded. I took the precaution to test each one by himself, 

 told him nothing of what I expected, or of the testimony of others. I made no 

 suggestions to any of them, but let each tell his own story. All told the same 

 tale ; one peculiarity all agreed to, the image in the glass was upside down from 

 what they saw with the naked eye. They would describe many peculiarities of 

 color which could not be seen by others with the aid of the glass. It should be 

 remembered that the "heater" has to see his iron in the furnace while it is en- 

 veloped in a flame whose intense glare prevents unskilled eyes from seeing any- 

 thing, an education of the eye peculiar to this class of workers, as no other class 

 of workmen is exposed to the same degree of heat or light. 



I noticed as soon as the eclipse had progressed some time that I became 

 nervous. I observed the same fact in many others about me. My wife at home 

 did not think of the phenomenon at first, but became so nervous that she had to 

 rush out of doors ; she then saw the eclipse for the first time. I found this 

 nervousness more in women than among men, chiefly in persons of debilitated 

 frame, such as convalescents. Is this magnetic ? 



In accordance with your request, I repeated the experiment of Ericsson, 

 and submitted a spherical piece of iron, eight inches in diameter, to a heat of 

 over 3,000 degrees, Fahr. It was carried to an almost melting point, withdrawn 

 from the flame and placed on a stand. It had the appearance of a disc at all 

 distances tried, up to over 100 feet. As seen by Mr. Hughes, the chief engineer 

 of the mill (one of the most scientific men in his line in the West), myself and 

 others, it was perfectly yftz/. The convexity did not appear; it was while in this 

 state, to all appearance no longer a sphere, but a disc. As the iron cooled off it 

 resumed its original appearance of a sphere. Our mill men were much surprised 

 by this phenomenon which they had been seeing all their lives, but till now had 

 never observed. 



Rosedale, Aug. 12, 1878. 



