Camphor towards the Light. 



369 



be quite sure of my instruments, I asked Messrs. Negretti and 

 Zambra to prepare two thermometers that should range together 

 with considerable accuracy. These instruments were received 

 during the very warm weather towards the end of July, and the 

 results obtained bv them struck me as remarkable. A cylin- 

 drical glass 10i inches high, arid nearly 3 inches in diameter, 

 was washed with sulphuric acid and an abundance of water, 

 dried, and charged with crude camphor. The thermometers 

 were suspended in the glass, front and back. The readings were 

 taken at first every five minutes. 



July 26, 186.2. Sun on w r est window. 



Remarks. 



Furthest. 



Time. 



Nearest 

 light. 



Remarks. 





74° F. 



5.40 p.m. 



74° F. 







83 



5.45 



83 



Slight misty appear- 





83* 



5.50 



83f 



ance in the glass. 





81 



5.55 



m 







79 



6.00 



79^ 







78 



6.5 



78| 



Clouds coming over 



Faint camphor depo- 



77 



6.10 



m 



the sun. 



sit. Moisture con- 



72 



6.15 



72 



Slightly clouded. 



densed high up on 



72 



6.20 



72 





one side near the 



76 



6.25 



76\ 





back. 



77 



6.30 



76 



Faint deposit. 





76k 



6.35 





Do. increasing. 





76 



6.40 



75 



Ditto. 





7o\ 



6.45 



75 







75 



6.50 



7H 



Deposit much more 





75 



6.55 



74 



marked than on the 





7H 



7.00 



73| 



other side, but still 





7oh 



7.10 



m 



faint. 





7% 



7.20 



72 







72± 



7.30 



7H 







7H 



7.40 



7H 







72 



7.50 



71 







71 



8.00 



70 







70* 



8.30 



69i 





Caudles introduced. 



71 



9.00 



70 







69 



10.00 



69 





Deposit all gone. 



66 



11.00 



1 



66 



Deposit all gone. 



The above results are remarkable. The camphor vapour, as 

 also the small amount of moisture left in the glass, are condensed 

 on the side furthest from the light where the temperature is a 

 little lower than in front ; but the most remarkable feature is the 

 scantiness of the camphor deposits, although there was an abun- 

 dance of light and heat. The deposits were almost nothing, and 

 at length they disappeared. The reason for this is that the 

 front and back temperatures are about equal. 



