Year: 1860

time have been given relating to the origin or
source of the subtle fluid or element. 1t had
been supposed to be produced by the friction
OF the currents Of air in motion; it had also
been attributed to growing vegetation; also to
evaporation 1t was well known that boiling
salt water produced electricity Steam blown
off from a locomotive was a source Of electric
ity; but IL was frietiOnal Upon the whole the
origin Of atmospheric electricity was not con-
clusiyely ascertained. There is a theory that
the atmosphere is not electrical per Sc, but
only by induction; that the earth is electric,
and the air only electric under certain cOndi-
tions. This was Pelcher's theory. IL had
been adopted by some European physicists,
and be must say that it had not received the
sttention it deserved The late DR. Hare of
Philadelphia, entertained a similar theory
that the earth was plus electrical and the air
minus.


1t was certain that the amount of electricity
in the air varied with the amount of vapOr
present. On clear, dry, clOudless days there
was but little electricity to be detected by the
electrOnometers; and il was only when We had
masses Of vapOr in the form of clouds that
there were electrical discharges If polished
iron rod, two or three feet in length, with a
polished brass or iron ball at both ends, be
held horizontally. there will be no sign of
electricity ! u the rod, but If ii be held verti-
calIy, it instantly becomes electrical. The
end nearest the earth will be plus electrical,
and the upper end minus. If the rod be held
near the ground, and then raised as high as a
man can reach, the electronometer indicates
change Of electrical condition; when near the
ground it is most electrical The electronom-
eter at the Smithsonian Institute showed great
changes in a few feet elevation. 1t had been
demonstrated that the electricity was repelled
by the atoms of matter composing the earth
into the air. He used the word repelled as
best expressing the idea. Ii rad also been
demonstrated that an atom Of electricity at the
surface of the globe acted in concert with the
globe itself in repelling a second atom of cleo
tricity outside the first. The repelling power
was inyersely as the square Of the distance
Prof Henry then gave the phenomena of ex-
plOsive atmospheric electricity.


WHAT CAUSES A THUNDER STORM.


No thunder storm can occur until there are
two layers of clouds. The electricity is carried
into the air by the masses of vapOr going up
from the earth. Vapor rising from the earth
always carries more or less electricity with it.
He had ascertained these and other interesting
facts from Mr.. Wise, the ballOonist, with whom
he had been in correspondence, and who had
undertaken experiments. Mr. Wise said that
in passing through thunder storm, he was
always first carried through dense cloud into
open space, with a second cloud hanging above
him Currents of air moved between the cloudy
layers in direction frequently transverse to the
current below the lower cloud. He had repeat
edIy been carried along by this transverse
current, and when npOn C0mIng down through
the lower cloud, he had again been caught by
the ascending current and whirled up again
Between the two clouds there were constant
flashes of lightning from the upper to the
lower These flashes were not explosive. The
heat lightning so often seen is the electricity
Of the upper cloud descending to the lower
The explosive discharges are always between
the lower cloud and the earth. Between the


- IL :.
always less dense than the lower, and always
less electrical.


thunder storm as it moved across the
country was sometimes constantly renewed by
the masses Of vapOr constantly ascending and
carrying up electricity from the earth in diff
fused particles t. be returned in explosive dis
charges. New vapOr carried up new electri-
city The French physicists thought that a
thunder cloud might be disarmed by running
up numerous points; il might be diSarmed OF
rendered harmless for a single locality, but as
the clouds passed on new electricity would be
sent up, so that to wholly disarm the thunder
was Impossible, for he had new resources always
at command.


BINOCULAR VISION.


The section of physics was much interested
BY lecture from Prof. William B. Rogers,
giving some experiments and infer ences in re-
gard TO binOeular vision. He eombatted with
great earnestnesS and warmth the theory of





combine the pictures of the object before il
which are made upon the retina, point by point.
This striking fact was stated. Let an object be
held in the hand and looked at attentively for
q minute, and the eyes then directed to a dis
tant wal. or screen, the room being dsrkened.
On closing one eye, an image of the object is
seen inclined in one direction on closing the
other it is seen inclined in an opposite direc
ton, showing that each eye had received upon
its retins an Independent impression or picture.
On looking with both eyes, the two pictures
unite, and the object is seen projected upon the
screen. This idea Of the independent action
Of the two eyes was verified by showing thai
the effect OF the stereOscOpe can be produced
by passing a card rapidly back and forth over
the surface Of the sterreograph, so that but
one of the twin pictures is seen at any given
ins tant; the two are united into one Just the
same as with the instrument, and il is seen
distinctly projected. Thus it appears that the
mind does much Of the work attributed to the
retina And that wonderful effect which we
call vision is the result of variety Of causes
other senses beside the eye playing an import
ant part. Thus the sense OF feeling, for exam
pie, by little practice we are able TO see two
pictures Of an object held in the hand, showing
that each eye has an independent picture; but
we commonly see but one, because the sense
Of feeling instructs US that there is but one,
and follows Its experiences.


The lecturer was greeted with general clap
ping Of hands as he sat down. In corrobora-
tiOn Of the interesting views presented, Leigh
Hunt mentioned a curious instance Of - seeing
double" Looking through lattice at barn,
in the front Of which was an open door, he saw
distinctly two doors ten or fifteen feet apart,
and his eyes persisted in seeing two. Nor could
he, for the life Of him, tell which was the true
and which was the false. The doctrine of Pro-
fsssor Rogers gives the explsnation--each eye
had picture of its own, and the slat of the
lattice separated the two, or prevented them
from being united beyond.


CAMBRIDGE BIOLOGICAL MUSEUM


Prof. AgassiI gave some remarks on an ar
rangement of a Geological Museum He said
that a museum indicated the condition Of
knowledge in = country. In regard 10 the
Cambridge museum he said the first beginning
was the so, 600 bequeathed by Mr.. Gray, fol,
lowed by SIS 900 from the citizens; also by the
State, 500, 900. With such support, he laid
out plan which in the end would be second
20 none in the world. One tenth part Of the
plan had been carried out, and the specimens
were being arranged.


He intended to avoid all the previous models;
they were antiquated, because they were sys-
tematic-not giving the progress Of science.