at the total solar Eclipse in 1882. 57 



bulb thermometer are much less, namely from 49*5° to 66'2° Fahr. 

 The temperature of the water of the Nile is very nearly the mean 

 of the maximum and minimum temperatures of the air above it. 

 These means were on the 



14th, loth, 16th, 17th, 18th, mean 

 77-5°, 74-5°, 79-0°, 79-5°, 82-75°, 78-65°. 



The temperature of the Nile is a little below this mean. The 

 large range of temperature in "the air is partly due to the cooling 

 effect of the evaporation from the surface of the water. 



The evaporation experiments were made on water contained in 

 a deep plate. It contained 400 cubic centimetres and exposed a 

 free surface of 243 sq. centimetres when full, and 230 sq. centi- 

 metres when nearly empty. It was set upon a tin cone which 

 raised it about 6 inches above the ground. The difference of the 

 effect of the sun upon the water and upon the sand close to it was 

 well shown on the 16th at 2 p.m. when the water in the plate had 

 a temperature of 82 - 5° F. while the temperature of the sand was 

 134° F., making a difference of more than 50° F. 



The following notes of the weather were made at the time and 

 are of use when taken in connection with the observations of the 

 calorimeter. 



16th May. — The sun rose in a cloudless sky and there was a 

 very light wind from the west. As the morning wore on, it came 

 round more and more to the north and freshened slightly. At 

 10 a.m. the wind seemed freshening and came in gusts, retarding 

 distillation. In the afternoon it was calm. 



17th May. — The day of the eclipse, the sun rose in a cloudless 

 sky and the inhabitants of Sohag had already begun to collect on 

 the banks of the Nile where they remained until the eclipse was 

 over. The temperature recorded as at 8.30 a.m. was really 

 observed 50 seconds after totality began, and I had no difficulty in 

 reading the thermometer although all the principal stars were 

 shining brightly, along with an unsuspected comet which appeared 

 with totality, between two and three sun's diameters from the 

 darkened disc and with a slightly curved tail quite as long 

 as the sun's diameter. This comet had not been detected before 

 and I understand that it was never seen afterwards. It was 

 a very striking feature of the eclipse to those whose occupa- 

 tions enabled them to look at it. I made a sketch immediately 

 totality was over. Perhaps the most impressive period of the 

 eclipse is during the two or three minutes that precede the total 

 phase. Until a very large proportion of the sun's disc has been 

 obscured the decrease of light causes no remark, especially from 

 people who are accustomed to climates where clouds are more 

 common than sunshine. But when the time comes that every 

 minute and indeed every second alters by many per cent, the 



