The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1896-06-28
HOW FAR CAN The
EARTH Be PENETRATED2
Proposition Made in France
to Travel in a Straight
Line.
Colonel Hennebert Gives Inter-
esting Facts Showing Its
Impossibility.
Mans Limit of Ascension Appears
Equal to the Depth He Can
Penetrate.

Under this title, Colonel Hennebert con-
tributes to La Nature paris, May 23) a
criticism of the proposition which, IL
seems, has been made in France with some
show of seriousness, to travel from place
to place in straight line by tunneling be-
meath the earth's surface instead of follow
ing along that surface, which compels us
at present to move in curve. Such tun-
mel, although accurately straight, would be
down hill" for half its length and "up
hill'' for the remaining half, hence most of
the distance GOULD be covered by means OF
gravity alone. Colonel Hennebert con-
cludes that this project is impossible of
realization, for reasons which will appear
from the following extracts, translated
from his article. After illusions to Jules
Verne's fantastic tale, "a Journey to the
Center of the Earth" he goes on to say:
This geographic romance is charming
from one end to the other, but it is after
all only a romance, and since people will
persist in desiring to penetrate the mys-
teries OF the interior of our planet it is best
to disabuse these curious adventures.
The best means to dampen their ardor by
means of curative douche is to demon
strate to them mathematically the impos-
sibility of a journey of this kind, an i'm
possibility that should have been revealed
TO them by their own intuition"
Colonel Hennebert tells US that M. Col
Egnon. French geometer, has recently
worked out mathematically the move
ment of a point on chord of the terres-
trial sphere: that IS, practically, the mo-
ton of a railway car, let us say. on rail-
way laid IN such a tunnel as we have sup
posed. AS may be easily seen, it would
move faster and faster to the middle of the
tunnel and then slower and slower to the
other end. This end would be reached if
there were no resistance, but the friction
of the wheels would stop the car at some
point between the center of the tunnel and
the farther end. Colonel Hennebert quotes
NJ. Collignon's conclusions as follows:
"At time when people are not afraid
OF long tunnels it would seem that there
would be a great advantage in employing
a means of locomotion in which gravity
would do almost all the work, and which,
by piercing the globe in straight lines,
would establish rapid communication be-
tween the most distant geographic points.
The characteristic of this mode of trans
port would be that the traveller would
always have TO descend to reach his OBJ
jective point, and that the journeys would
all take the same time, no matter what
the distance might be-"
Colonel Hennebert calculates this time
(which is of course, done on the SUPPOSE
ton that there is no friction), and finds
that it is AZ minutes II seconds, which
e., +r.,o
from London to Melbourne, or from Paris
to Timbuctu. However, it appears that
an important practical consideration has
been hitherto overlooked. Says Colonel
Hennebert:
I'VE hasten to declare that a journey of
this kind belongs TO the domain OF the i'm
possible. Without stopping to consider
the mass of objections that might be OPP
posed to his calculations, M. Collignon
sees an absolute obstacle to the realization
of his plan in the enormous pressures that
would be developed in the air at the depths
that would have to be reached in the
course of journeys at any length"
A table, showing the number of atmos-
pheres corresponding to the pressures at
different depths is here gwen and shows
that at depth of only fiftieth OF the
earth's radius the pressure would be repre-
scented by the number 34,5 SAT followed by
81 ciphersl The article goes on:
I'VE must then admit that in the whole
central part OF the tunnel, if it has pene-
trated to any depth in the subterranean
strata, there is a sort of impossible wall,
formed by pressed air, in which bodies
from the surface of the globe would be
stopped, crushed, perhaps burned up.
''To what depth beneath the sea-level
can we descend in pit freely open to the
air? 1t can be shown that the pressure of
three atmospheres is the extreme limit of
pressure that can be borne with impunlty
To this limit corresponds the depth OF
$3.50 meters (28,700 feet, or more than 500
miles), and when this has been reached
the first fifth of the earth's crust has
scarcely been traversed. This depth is yet
far from having been reached, even in the
most famous mines.
att is curious fact that this number of
$3.50 meters also nearly expresses the limit
of height to which we have been able to
rise in the terrestrial atmosphere.
"From all these considerations we can
conclude that within the limits of less
than nine kilometers, either above or
below sea level, by series of the most in
teresting conditions man sees himself con-
fined by the fateful decree: Ne plus ultra /"
A Suggestion for Inventors.
When electricity was first adopted in