1878. ] The Beneficial Influence of Plants. 807 
skeptical that aqueous vapor furnishes a very effectual barrier to 
terrestrial radiation. 
he tropical torrents can be accounted for by the property 
vapor has to absorb and radiate heat, thereby condensing the 
vapor raised from the equatorial regions through the direct rays 
of the sun. But it is only the upper strata of the vapor bed cov- 
ering the surface of the earth, which by radiating into open 
space produces the effect above stated. Owing to the same 
quality may be explained the formation of cumuli; the theory of 
sereim, or the falling of the exceedingly fine rain shortly after 
sunset in the fine season. These and many other meteorological 
phenomena receive their sqlution from the development of this 
property of aqueous vapor. Every one will readily acknowledge 
that a question affecting so materially important sciences as the 
one under consideration, should be quite definitely settled, and it 
is for this reason that so much stress, by way of testimony, has 
been here placed upon it. 
Admitting then that the vapor in the air does, by the property 
above discussed, influence numerous climatic conditions,’ the 
sources of this vapor certainly should claim a larger share of 
attention. 
Nature’s chief means of furnishing this moisture is through 
vaporization from the ocean, especially in the tropics; but many 
tracts of country inland, or even near the great seas, do not, for 
some reason, contain sufficient moisture. Now, if by any means 
at our command we can assist nature in supplying this very 
essential substance, it would be well worth our endeavors. Here 
the question presents itself, “ Is there any connection, all things 
considered, between the proportion of moisture in the air and 
forest growth?” This question has been the subject of a great’ 
deal of discussion among able scientists, and we believe the bal- 
ance of argument is in favor of the theory that there is a relation- 
ship existing between vegetation and the humidity of the air. 
The writer hopes he may have been successful in showing that 
a large proportion of the atmospheric vapor may be accounted 
for through the process of transpiration from plant life, that is, 
where there exists a fair percentage of woodland, say from 
twenty-five to thirty per cent.; so that now the above query may, 
we think, be answered in the affirmative. Under these circum- 
stances the practice of forest culture as a means of improving 
atmospheric conditions, cannot be too highly commended. 
