362 On a solar Calorimeter used in Egypt 



connection with this it may be recalled that the eclipse of 

 1 7th May, 1882, repeats itself after 19 years on the i/th May, 

 1901, with this important advantage, that in place of seventy 

 seconds the maximum duration of totality will be six minutes 

 and a half, and it will occur very nearly at noon at stations in 

 Sumatra and Borneo. 



The 1 8th May was the hottest day experienced. Perfect 

 calm reigned until 2 p.m. when a breeze began to blow up 

 the Nile and continued throughout the afternoon although it 

 was never very strong. During this forenoon the maximum 

 results were obtained with the calorimeter and the temperature 

 of the air reached its maximum 105 F. at 2 p.m. It will be 

 noticed that the temperature of the wet bulb thermometer 

 was only 65, or 40 F. below the dry bulb ; the air was of 

 extraordinary dryness. One effect of a climate such as this, 

 where great dryness is associated with very high temperature, 

 is that, although perspiration is abundant, the skin is never 

 moist, indeed it is so dry that it has a tendency to crack. 

 Another remarkable subjective effect of high air temperatures 

 such as those of the afternoon of the i8th is the notice given 

 when the temperature of the air passes from below that of 

 the human body to above it. It is a matter of common 

 experience that in preparing a warm bath, very slight differ- 

 ences of temperature can be appreciated by the hand when 

 the water is at or about the temperature of the human body. 

 With air the conditions are different ; the capacity for heat of 

 all the air that can at any moment touch exposed portions 

 of the body is very small and produces no noticeable effect. 

 But although it cannot do so directly it can do so vicariously 

 for instance through the metal rim of a pair of spectacles. 

 The calorimetric work described in this paper necessitated 

 continuous exposure to the rays of the sun which were being 

 collected and measured, and in order to protect the eyes from 

 the intense glare of the sun it was prudent to use neutral 

 tinted spectacles. The moment the temperature of the air 

 passed upwards through the temperature of the skin was 

 signalised by the spectacles feeling hot. Although the tem- 

 perature rose to 105 F. the capacity for heat of the rim of 



