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or another of solar photography, and with only a minute in 

 which to make them. The principal stars, as well as the 

 comet, were shining brightly during totality : nevertheless, 

 I was able to read the scale of an ordinary thermometer 

 during totality. Two solar protuberances were visible to the 

 naked eye, but to me they appeared to be notches in the dark 

 disc of the moon through which red light was visible. This 

 observation has an important bearing on the interpretation of 

 the phenomenon generally called " Daily's beads." Of all the 

 natural phenomena which I have had the opportunity of 

 witnessing, there is none which produces so powerful an 

 impression as a total eclipse of the sun. 



Conditions during the forenoon of i8th May, when the 

 maximum value of the solar radiation was observed with the 

 calorimeter 362 



Discussion of the observations 363 



Rates of distillation observed on i6th, rythand i8th May: 

 Table III ... 3^4 



Graphic representation of the same 369 



The weather on each of the three days was very fine, but 

 it was best during the forenoon of the i8th, when the 

 maximum rate of distillation observed was i'5oi cubic centi- 

 metre per minute 370 



To transform i '5 gram of water at 100 C. into steam of 

 the same temperature 803 gram-degrees of heat are required ; 

 and this is the greatest amount of heat which has been 

 collected by the calorimeter in one minute. The actual 

 collecting area of the reflector is 903^5 square centimetres. 

 Therefore, the heat so collected is equivalent to 8888 gram- 

 degrees per square metre : and 8888 gram-degrees C. suffice 

 for the generation of i6'6 grams steam at 100 C. Therefore, 

 it has been shown by our experiments that, by the use of 

 ordinary mechanical appliances it is possible, under favour- 

 able geographical and meteorological conditions, to collect, 

 on a square metre of surface, at or near the sea-level, exposed 

 perpendicularly to the sun's rays, the energy of generation of 

 i6'6 grams of steam per minute, or 8888 gram-degrees of 

 heat, which are equivalent to 3777 kilogram-metres of work : 

 and, as this work is done in one minute, the agent is working 

 at the rate of at least 0-84 horse power. Therefore, the 

 object for which I designed the calorimeter and used it in 

 Egypt was achieved. 



Taking the area of a great circle on the earth's surface to 

 be 1 29-9 x io 12 square metres, the useful energy received by 



