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10 PHILOSOPHICAL SOCIETY OF WASHINGTON, 
With relation to the city of Washington, it was suggested that 
the Washington monument would afford a good opportunity (by 
placing illuminated fly-traps at different elevations on its exterior) 
for ascertaining the height at which mosquitoes fly, or are brought 
by the wind from the adjacent Potomac flats. The proposed re- 
clamation of the flats could scarcely do more than mitigate malarial 
disease, so long as our summer and autumn southern breezes come, 
laden with mosquitoes, from the miles of unreclaimed swamps 
farther down the river, as at Four-mile Run and other nearer local- 
ities. 
Mr. Bruuincs remarked that, since ague did not invariably 
result from insect bites, the most that could be claimed was that 
they accomplished an accidental inoculation with malarial poison. 
The subject was also discussed by Messrs. DoouirrLe, ToNER, 
and ANTISELL. 
The meeting closed with an exhibition by Mr. C. E. Durron of 
a series of oil paintings illustrative of the Hawaiian Islands. 
230TH MEETING. Fresruary 24, 1883. 
Vice-President Briiines in the Chair. 
Thirty members and visitors present. 
The Chair announced the election of Mr. Taomas RussELtL to 
membership. 
The first communication was by Mr. G. K. GitBErt on 
THE RESPONSE OF TERRESTRIAL CLIMATE TO SECULAR VARIATIONS 
IN SOLAR RADIATION. 
[ Abstract. ] 
Secular variations of climate may theoretically be catised (1) by 
the internal heat of the earth and (2) by changes in the constitu- 
tion or volume of the atmosphere. They have unquestionably been 
wrought (3) by changes in the limits and configuration of ocean 
bottoms and land surfaces, (4) by changes in the movements of the 
earth with reference to celestial bodies, and (5) by variations of 
