Crawford avalanche. (Grayling, Mich.) 1879-19??, 1892-11-24

| ly illustrated by its analogy TO hydrau-
lies, and Mr.. II. G.. Davis gives these
easily understood definitions OF electrical
terms: Volt, unit Of pressure, called
electromotive force, corresponding to
pounds of steam OF water pressure; am
pere, unit of quantity, called current,
corresponding to gallons of water; ohm,
unit Of resistance, similar to friction;
todtt, unit Of energy consumed, TAG watts
being equal to one horsepower, as is 49,
coo foot pounds. Substitute dynamo
for pump, wire for pipe, and electricity
for water, and conception Of electrical
transmission is at once clear as to its elc-
| mentary phenomena. Bracketing analo-
gous electrical terms, we may say that
certain number of pounds lvoltsl OF
pressure are required to overcome the
friction [resistanoel of the pipe [wirel in
order that the water [current may flow
at the rate OF so many gallons [amperesl
per minute. The larger the pipe wire
the more water currcnt] can be carried,
and the less will be the friction resist
ANGEL. Manifestly the pipe [wire] might
be so small that the friction [resistancel
would absorb very large proportion of
the power of the pump [dynamo, leaving
but little remaining for useful effect,
| therefore the two horns OF the dilemma
are-if the pipe [wire] be too large it will
cost too much; if too small, the loss will
be too great.
Frederick j. Smith, of Trinity College,
Oxford, explains a curious way of find
ing the depth of piece of water at dis
lance. "About two years ago." he says,
~ wished to know from time to time the
rate at which river was rising after a
fall of rain. The river was consider
able distance from the spot where its
height was to be known. BY means of
the combination of two organ pipes and
telephone circuit described in the fol-
lowing lines / have been able to make
the required measurement within rather
close limits. At the river station an or
gan pipe was fixed vertically in an in
verted position, so that the water in the
river acted as stopper to the pipe, and
the rise or fall of the water determined
the note it gave when blown by small
bellows driven by very small water
| wheel. A microphone was attached to
the upper end of the organ pipe; this was
in circuit with wire leading to town
station at some distance; at the town sta
ton there was an exactly similar organ
pipe, which could be lowered into YES
sci full of water while it was sound
ing BY means of the telephone the
note given by the pipe at the
river was clearly heard at the town
station; then the organ pipe at this
station was lowered or raised by hand
until it gave the same note. The lengths
of the organ pipes under water at the two
stations were then equal, so that the
height of the water in the distant river
was known. The determination can be
made in less than minute by any one
who can recognize the agreement of two
similar notes. The arrangement when
first tested was so placed that the height
of water at two places near together
might be easily compared. found that
lad with an average ear for musical
sounds was able to get the two heights
to agree within one-eighth of an inch of
each other, while person with an edu-
Gated ear adjusted the instrument i'm
mediately to almost exact agreement.
The total height to be measured was sew
entecn inches. A difference of tempera-
ture ut the two stations would make
small difference in the observed heights.
For instance. taking note caused by
80 vibrations per second, difference
of 10 degrees G. between the tempera
ture of the two stations Zone not likely
to occur would make difference of
about 0.02 feet in the height, a quantity
of no moment in such class of meas
urements. The organ pipes were of
square section and made of metal to
resist the action of the water. Mature.
How NATURE PRODUCES RAIN.-Man
may not hope to assist nature in the for
| nation or prevention of rain until he
better understands the details of natures
own methods. The ideas most widely
accepted, at present, as to the natural
process of the formation Of rain, 60 only
| so far rs to say that the moisture present
in the atmosphere is extracted from the
air by three different steps, namely, first,
| the saturation with aqueous vapor that
| is produced by cooling the air; second,
| the condensation of the vapor into small
visible particles of cloud and fog; third,
the agglomeration of these droplets of
water into drops large enough to be pre-
/. The ordinary natural methods of ac-
complishing the cooling required in the
first of these steps are: (a) the mixing of
cold and warm air by which, however,
only very slight amount of precipita-
ton can be formed; (b) the radiation
of heat to the colder earth and
air ami space by which at first
thin layers of fog or stratus clouds
are formed which then slowly thicken
with time; (c) the rise and expansion of
large masses of air; the mechanical work
done by the expansion simultaneously of
the whole mass may cool it to any extent
whatever. This last is the important
process on which all our rain depends.
III. The second step, namely, condensa-
ton, is a molecular process that has
been likened to the capitalization of
solid salts from liquid solutions, although
there is too little known abo t either
process to warrant the belief that they
are really similar. Aitken and others
maintain that the condensat' on of vapor,
like the capitalization of salts. demand
some nucleus as starting point, and
that every minute droplet of fog or cloud
must have particle of atmospheric dust
rs its initiative. III. The third step in
the above process of rain and formation
is the agglomeration of fog or cloud par
ticles into larger drops. About this there
is very little known from actual observa-
ton, and the hypothesis are quite vari-
gus. The hypothesis that among these
particles some are larger than Others and,
by their more rapid descent, overtake
| tho amallar ones and Tins fyrow larUpr as