3.38 4.50 3.52

Average for the six months, 22.25.

It will be noticed, that the average for the month of August is about 33
per cent. larger than for June and July. The quantity of rain falling in
each month, as registered at the Cambridge Observatory, is as follows:

MEAN OF OBSERVATIONS FOR TWELVE YEARS.

_Jan._ _Feb._ _Mar._ _Apr._ _May._ _June._
2.39 3.19 3.47 3.64 3.74 3.13

_July._ _Aug._ _Sept._ _Oct._ _Nov._ _Dec._
2.57 5.47 4.27 3.73 4.57 4.31

_Spring._ _Summer._ _Autumn._ _Winter._
10.85 11.17 12.57 9.89

Average quantity per year, 44.48.

The quantity falling from January to July, is much less than falls from
July to January.

The great quantity of snow which falls in New England during the Winter
months, and is carried off mainly in the Spring, usually floods the low
lands, and should be taken into account in establishing the size of pipe
to be used in a system of drainage. The following observations of the
average depth of snow, have been made at the places cited, and are
copied, by Blodget, from various published notices:

Oxford Co., Me. 12 years 90 inches per year.
Dover, N. H. 10 " 68.6 " "
Montreal 10 " 67 " "
Burlington, Vt. 10 " 85 " "
Worcester, Mass. 12 " 55 " "
Amherst, " 7 " 54 " "
Hartford, Conn. 24 " 43 " "
Lambertville, N. J. 8 " 25.5 " "
Cincinnati 16 " 19 " "
Burlington, Iowa 4 " 15.5 " "
Beloit, Wisconsin 3 " 25 " "

One-tenth the depth of snow is taken as its equivalent in water, for
general purposes, though it gives too small a quantity of water in
southern latitudes, and in extreme latitudes too great a quantity. The
rule of reduction of snow to water, in cold climates, is one inch of
water to twelve of snow.

The proportion of the annual downfall of rain which is collectable into
reservoirs--or, in other words, the per-centage of the rain-fall which
drains off--is well shown in a table used by Ellwood Morris, Esq., C. E.,
in an article on "The Proposed Improvement of the Ohio River" (Jour.
Frank. Inst., Jan., 1858), in which we find, that, in eighteen series