i879-] 
A New Theory of Dew, 
471 
Silica 21*6 
Lime 13*2 
Iron protoxide 65*2 
100*00 
The details of the calculations are given at length in the 
memoir, which is accompanied by a description of the mi- 
croscopical examination of thin sections of the lavas by 
Prof. Hull, and a coloured plate giving the more marked 
peculiarities. We trust that the principle of least paste 
will hereafter be applied to the lavas of Etna, the Lipari 
Islands, Iceland, and Hawaii. 
Addendum . — Towards the end of last month, when Etna 
was in a state of violent eruption, Vesuvius showed signs of 
an increase in dynamic activity. A telegram from Naples, 
dated June nth, states that “ A slight eruption has com- 
menced to-day from Mount Vesuvius, and is gradually 
increasing.” A private letter from Naples, dated June 16th, 
contains the last piece of news which we have been able to 
collect concerning the present condition of Vesuvius : — 
“ It shows some small activity at the summit. The upper 
crater is full of liquid lava, which at times boils over, and 
sometimes also is thrown up, but no great amount of force 
is to be observed.”— R. 
III. A NEW THEORY OF DEW. 
f NVESTIGATIONS which Prof. Levi Stockbridge has 
made at the Amherst Agricultural College, upon the 
comparative temperature of soil and air, and the dis- 
position of dew upon the earth and plants, have led him to 
conclusions very different from those commonly received in 
regard to the formation of dew. It is usually held that dew 
is the moisture of the air, condensed through contact with 
objects of a lower temperature, and that it does not form 
till radiation has reduced the temperature of the earth and 
other obje( 5 ts below that of the atmosphere. The experi- 
ments referred to seem to indicate that, as regards objects in 
the immediate vicinity of the earth, at least, the process is 
