36 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
In reply to a question by Mr. AntiseLt, Mr. Dawu said that 
little was known of the humidity of the interior of Alaska; 23 
inches of precipitation, nearly all in snow, had been observed in a 
single year at one point and 12 inches at another. 
Mr. F. B. Hovueu then read a paper on 
THE CULTIVATION OF THE EUCALYPTUS ON THE ROMAN 
CAMPAGNA, 
which was discussed by Messrs. E. B. Etuiorr and H. FarquHar. 
It is published in the American Journal of Forestry for June, 1883. 
235TH MEETING. May 5, 1888. 
Vice-President Briir1nes in the Chair. 
Twenty-seven members and visitors present. 
The Chair announced the election to membership of Messrs. 
Wixi1AM THomas SAMPSON, JOHN OscAR SKINNER, and THomaAs 
CROWDER CHAMBERLIN. 
The first communication was by Mr. H. A. Hazen on 
HYGROMETRIC OBSERVATIONS. 
[ Abstract. ] 
After describing the various devices by which the moisture of. 
the air has been measured, and especially the novel and valuable 
apparatus of Crova, the speaker illustrated the difficulty of the 
subject by contrasting synchronous determinations made at four 
points within a radius of two miles, and then described some ex- 
periments tending to show the inaccuracy of the wet and dry bulb 
hygrometer, as ordinarily observed. The value of the wet bulb 
reading is enhanced by blowing on the bulb with a bellows, or 
otherwise subjecting it to a brisk current of air. . 
Mr. Harkness remarked first, that Mr. Hazen’s experiments 
appeared to prove the insufficiency of Regnault’s formula, for they 
showed the difference between the indications of the wet bulb and 
dry bulb to be a function not only of the humidity, but of the 
velocity of wind; second, that height of station above the ground 
