Snow is often called the "poor man's manure;" and if it is true that
it has any manurial value, the farmer's prospects for the next season
are certainly flattering. The body of snow upon the ground in all the
Northern and Middle States is very great, and millions of acres of
land are covered by it as with a blanket of the whitest wool. It is
probable that seldom, perhaps never, has so wide an area of our
country been covered as during this month of January, 1877. The
question whether snow is capable of affording to lands any of the
elements of fertility is one often asked; and in reply, the Boston
_Journal of Chemistry_ says that it probably is. The atmosphere holds
ammonia and some other nitrogenous products, which are without doubt
brought to the soil by snowflakes as well as by rain drops.
Experiments both here and abroad would seem to prove the truth of this
conclusion.

Rains are not only valuable for the moisture which they supply, but
for what they bring to us from the atmosphere. During a thunderstorm
nitric acid is produced in considerable quantities; and dissolved in
the rain drops to a high degree of attenuation, its effects upon soils
are highly salutary, as the nitrogen permeates the entire soil.

* * * * *

ACTION OF SEA WATER ON LEAD.

The _Journal of the Chemical Society_ says that freshly cut strips of
lead were kept in a bottle of sea water for four days, the bottle
being frequently shaken. No trace of lead could be detected in the
water, but the bright surface of the strips was coated with an
insoluble lead compound. Hence lead pipes may be used in marine
aquaria without any fear of injury to their inhabitants.

* * * * *

PAPIN'S STEAM ENGINE.

BY PROFESSOR CHARLES A. JOY.

It is a matter of history that, as early as 1688, Denis Papin,
Professor of Physics and Mathematics at the University of Marburg,
proposed to substitute steam for powder in the engine invented by
Huyghens, and that in 1695 he published a description of several new
inventions, in which steam played an important part. The Elector Carl,
of Hesse-Cassel, was anxious to be free from the annoyances and
impositions practised upon his boatmen by the authorities at Muenden,
and he proposed to avoid that city by constructing a canal connecting
the Weser with the river that flowed through Cassel. Much of the work
was accomplished, and the half finished line