372 Mr. Fox v)i the late Solar Eclipse. [Nov. 



Article VII. 



Observations on the late Solar Eclipse. By Mr. James Fox. 



(To Dr. Thomson.) 



SIR, Plymouth, Sept. 23, 1820. 



Lat. 50° 22' 24" N. Long. 4« 12' 45" W. 



Believing the recent great eclipse of the sun must have 

 excited general attention, 1 am induced to send you the result of 

 some observations I made with a view of ascertaining its effect 

 on the temperature of the atmosphere, as well as to note the 

 precise time of its commencement and duration, as seen from 

 this place. The method taken to obtain the temperature was as 

 follows : 



For three successive days, viz. the 6th, the 7th (the day of the 

 eclipse), and the 8th inst. I placed a Fahrenheit's thermometer, 

 as well as a Leslie's differential one, i)i the sun, and also another 

 of Fahrenheit's in the shade, and noted their respective indica- 

 tions at intervals of five minutes. The great coincidence of the 

 thermometer in tlie shade on these days (except during the time 

 of the eclipse) afforded a very satisfactory proof that the temper- 

 ature of the period was nearly equal, and consequently became 

 a tolerably good standard by which the loss of heat at the time 

 of greatest obscuration might be ascertained. By this it 

 appeared that the loss of heat at the time of greatest obscuration. 



By Fahrenheit in the shade, v/as 45° 



By ditto in the sun 13-0 



By Leslie's differential thermometer in the sun. 16-0 



By means of a three and a half feet telescope, and a watch 

 accurately adjusted by repeated solar observations, I found the 

 eclipse to end precisely at 2*" 58' 56" p. m. apparent time. I am 

 sorry clouds intervened at its commencement so as to prevent 

 my seeing it until too late to note the time. 



The loss of light did not appear so great as was expected : 

 the darkness did not exceed that of a very cloudy day. 



I am. Sir, 



Your obedient servant, 



James Fox. 



