New Orleans Republican. [volume] (New Orleans, La) 1867-1878, 1873-08-17
FoRsHEY's LECTURE
LATITUDE Observation-Disclosures

Professor c. G.. Forshey having been
called away from the city on important
public business, and being, in consequence,
unable to keep his engagement to adore Sc
the young men of the Polytechnic 1nsti-
tute, has forwarded to us the manuscri pit
of the lecture he would have delivered
which we take pleasure in laying before
our readers in general, and the young men
of the class in particular. This lecture was
to have been the fourth Of the seriee:
Cadets of the Polytechnic Class-At the
close Of our last lecture ION iron ! IN
formed you that official duties would keep
me on levee survey for some weeks hence;
and that my lectures, mean time, would ne
cessarily be suspended. If, however, any pa
per in New Orleans will print them for me
and you and the public, will continue the
lectures during my absence. But my sub
jects will, in Difference to my greater and
more varied audience, be less exclusive. II
not less interesting and instructive.
The subjects named above nave nave
been prompted by facts and observations
on the way, which l have had occasion to
explain to my young engineer friends.
Come travel with me and them. OF course
have had no access to Books and authOrl-
ties, and have to conine myself to the
superficial science carry in my head.
You have all studied geography, and
know probably that New Orleans is exactly
on latitude 300 north, and, singularly
enough, exactly on the ninetieth degree
West of Greenwich (LondOn); so that our
great CITY is one.ttird the distance from
the EQUATOR to the pole, and One-quarter
the distance round the earth, or six hours
in time from the universally agreed starting
point of longitude, for all mankind. Don't
forget this remarkable fact, for some day I
shall hope to introduce you to an observa-
tory, built upon this extraordinary point OF
intersections; perhaps we shall build your
Mechanical college around this observatory
Ascending the Mississippi river two humid
red and five miles, say three miles above
the mouth of Red river, we find the thirty
first degree of latitude crossing the river
and forming the boundary between Louisi-
ana and Mississippi on the eastern extern
sion, and forming the basis parallel for
United States land surveys on both eides of
the river. 1t is, in many respects. en inter-
esting line.
In the early day it formed the boundary
between the British and Spanish posses
sions, east Of the river, ard was the south
limit of the lands claimed by the ChOctav
nation Of Indians. 1t was originally estab-
lished BY Sir William Dunbar, the British
geographer general-a learned man who
settled home still known as THE Forest"
on second creek, q few miles from Natchez,
and left his descendants, some Of the best
and most respectable people OF that region.
After the admission OF Mississippi as =
State, say about 1915, Mr.. Ellieott, the
noted astronomer, was sent by President
Madison, to establish and survey this line.
He spent some months Of the most care
full observation upon the bank Of the river,
at this point, and established monument
on the summet of the bluff. just back of
| what is now known as the Ackland planta-
ton. He cut away the forest, leaving an
avenue through the trees, still visible in
the year 1910, when it was my fortune to
have to revise this portion Of the time.
In order to establish the basis parallel
on the west side of the river, sought tor
the lane in the forest on the east, which en-
abled me to discover the monument, pyra-
midal block Of stone planted in the ground,
! and engraved ON the north side "Mississip
pi," on the south louisiana" and on the
| top Latitude 49," Correcting the varia-
| ton of my needle by this line l traced it to
| the river, planted my flags on the west side,
| ran into the deep forest of cottonwood
trees, the sloughs and thickets, and found
a few well marked trees, chopped by the
| United States survey, or on his basis paral-
| lei, which ran through to the ''Old river.
| known as Shreeves' cutoff.
Here the course cut the Old river lake
| and Turnbulls island, and again cut the
| late river third time, leaving half the
island on each side. AS a young engineer,
| felt some pride in having occasion to re-
| wise and reatfirm the work done by one
| whose history and ability had learned to
| admire and venerate. Even the AK marks
| as scars on the old forest trees appeared to
me to be half sacred as l traced this noted
| line in the deep solitudes of Louisiana
From Pearl river, in Mississippi, to the Sa-
| bine, in Louisiana, it is the most important
line known to the geographer; and to nearly
| every one it is notorious that it forms the
almost universal limit of cane production
northward, and to a great extent the south
| ern limit Of the cotton crop southwark
The few exceptions, perhaps, only confirm
the RUE.
| But what do you ask has all this to dc
with lightning Let us see. After leaving
this interesting locality our boat made d.
rectly for Fort Adams, then in sight, eight
miles due northeast. A dark cloud was
| hanging over the lofty hills that line the
river, 200 feet high. And that cloud was send
ing down straight shots OF lightning upon
the hills. We tied up to avoid the storm
Now, do you know any difference between
straight down shots of lightning and others!
! This difference is important. The etfor,
constantly made by nature is in heat and
electricity to restore equilibrium and bal
ance. Electricity. like heat, is either active
or latent.
| The condensation of the vapor or water
| in wonder cloud sets free the latent electric
| ity; and thus overcharges the cloud. II
rushes together, and takes the shortest
route to the localities least charged. On
| its way it will travel along conducting
| bodies, or along the line of least electricity
| <ho a. voU;np ho v,oncb fha N fb6
earth beneath, it will dart downward. and
on it's way will generally be bent more OF
| less, sometimes very sharply, to trave
along this line of least supply or of best
ccnduction. A lightning-rod or wet tree
or a very humied route through the air
will determine it's direction.
But, if the cloud region, as often happens
| be not overcharged, the electricity set free
| by cOndensing clouds, will shoot into other
portions of the cloud; often very zig zig
| and fading out, as it dissipates in the Othel
portions of the cloud less charged. Wher
this happens you have no violent, crashing
| thunder.
| But when the flash goes down to thu
earth it cumulates on the way down, and Ii
| followed by violent and jarring thunder
| This lightning is dangerous; the other en-
tirely harmless. In the former case, which
you will soon distinguish in storm, avoid
the shelter of trees, especially tall ant
naked trees. Green trees are much more
dangerous than dead ones, because the SAL
| and moisture of the inside forms a con
ductor. just as dripping water on the out
side. Ii on prairie, or treeless fields OF
| plains, lie down during thunder crashes
Lightning generally has double sparks
often three or more; but rarely one sparl
alone. These, if descending, follow eacf
other with the same track, even to thu
sharp angles. Occasionally the spark il
long enou gh to look like a stream of fire
but spark makes an impression upon the