660 The Temperature of the Sun. [October 
tion disproves the statement that the sun’s effective tem- 
perature does not exceed 1500° C. It is demonstrably over 
1800° C., and may for anything here shown to the con- 
trary be indefinitely greater. 
(2) The solar heat-radiation, so far from being com- 
parable to furnace heat, is at a minimum something like 100 
times that from melted platinum, area for area, and probably 
much greater. 
(3) The solar-light radiation (which offers a more trust- 
worthy indication of the total difference between the sum 
of all degrees of radiant energy than the heat) is over 5300 
times that from a temperature above that of melted 
platinum. 
(4) Since all the above results are simple statements of 
the fadfs of experiment, and are independent of formulae, we 
conclude that the formula of Dulong and Petit (which from 
well-condudted experiments, like those of M. Violle, deduces 
conclusions which trial disproves) must be itself wrong. 
Further, since this formula contains no term depending on 
the wave-length, it takes no account of the difference here 
proved to exist between the relative quantities of heat and 
light radiation from sources of high temperature, and is thus 
found especially untrustworthy at those temperatures at which 
it has been most frequently applied. 
I do not yet venture an opinion of my own on the real 
temperature of the sun, further than that I think it much 
higher than has been of late believed. 
The preceding observations and inferences all seem to 
point to the use of the highest attainable terrestrial tem- 
peratures ( e.g ., that of the eledtric light) in comparisons 
(and the consequent least dependance on formulae) as the 
safest line for future investigation. 
