New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1869-07-15

n, tbe surveying signals which the instrument registers
automatically according TO tho angular h
resH Cheyaer obtained by by causing vertical
mako the tour OF the horizon by means OF cookwoTk
aed around the station These images are thrown 6y
OF rejecting prism in rigid connection win the
lens through a slit placed above horizontal sensitive
plate The axis Of this slit forms part OF the movable
vertical plane, which contains az once tne opuca AXIS
muth The slit opens automatically and without viora
tiOn after the lens and the prism haFe already ACQUIRED
uniform rotary movement When the tour OF the hOrl-
zon is finished the slit closes OF itself and the whole ap
parans may be turned horizontally until the needle Ola
com pass attached comedies with the zero upon It's disk
then by opening aperture specially constructed Tor
the purpose the light is allowed TO trace on the margin
OF the plate line indicating the picture the direction
OF the magnetic meridian. This precauton serves TO
give the direction to the negative and allows the drafts
combinations Of subsequent tours Of the horizon.
In this circle Of Photographic images all the signals
ton as seen from the station In cases where the
signal too high or too low in relationto the instrument
a small lens, movable round horizontal arm fixed upon
the apparatus, allows OF recording this signal upon
landmark in the field OF the instrument Finally hair.
line, produced by means OF thread situated at he
hight OF the optical axis shows ell the points In the pho
tographc panorama In which the hight equal TO that
the apparatus requires other special knowledge than
that Of photography. To comprehend the great sim
us repeat the details Of the methods hitherto used
After having with considerable tronble directed the
upon each signal the figures Of the levels are taken down
in succession When the levels are very numerous sew
horizon. protractOr is placed In position, and,
after having been noted s directed in succession TO eacn
horizontal angle These several operations are very ons
and tedious and often committed when are
difficult TO correct the higher they mount up Inc
ordinary theOdote is only really preferable when ~ -
desired 70 obtain the most precise results by calculating
the construction OF each triangle. n,
On the other hand the Photographic plane VIII
complete tour OF tho horizon within half an hOuf anu
the number Of signals may be multiplied WITHOUT III HnS
rendering the task mere labOrous by increang INC
number OF original signals there is less risk OF error ana
Of subsequent rectcation, and much interediate VOTE
and calculation obyiated Less and skill arc required
In It's employment and inclemency OF weather DeoOmesa
matter OF little Importance. The Comhee stato la'
the instrument has already used with great adyan
tage, and in have been discovered III
standard maps by its They say IN conclusion that
after twelve OF ncessant study Mr. CheVaer mas
died at the moment when he had hoped 10 see MS Ne-
ton adopted by learned bodies and suggest mat 80
novel and Ingenious an application should be hOnored by
the high appreciation OF the Academy OF sciences
THE SPEED OF ELECTRICITY THROUGH
LAND Misunderstanding TO observations made by u.
Davidson Astronomer United States Coast Survey on
the night Of the 2sh Of February 1862 at San Francisco
California on a loop OF telegraphic wire extending
thence 10 Cambridge Massachusetts, and returning TO
San Francisco the return signal being receiver on
chronograph that receiving the outgoing signal
was found the total interval OF time between the
two signals Amounted 10 eghttenths or one second Inc
entire wire was divided into eleven portions, OF ABOUT
ESQ miles each. aud connected by repeaers which sent
from one portion 20 the next new electric current
having greater speed than the original one would nave
had n continued beyond the first reach OF $50 miles 10
will that the actual rate OF transmission OF each
current over miles cannot be deduced from these
data by dividing the whole time by H. but we are AS
sured that the practical speed OF series OF currents
combined by relays at the rate OF 1900 miles IN Oo Oi