One phase of the construction of tunnels through the Alps was recently
discussed by M. Brandicourt, secretary of the Linnæan Society of the
North of France, in the columns of La Nature. He showed that only a
few thousand feet below the eternal snows of that region so high a
temperature may be found that workmen can scarcely live in it. Nearly
all of the other difficulties encountered in those enterprises had
been foreseen. This one was a great surprise. It shows how the
interior heat of the earth extends above sea level into all great
mountainous uplifts on the earth's surface.
During the tunneling of Mont Cenis, says M. Brandicourt, the
temperature of the rock was found to be 27.5 degrees C. (81.5 degrees
F.) at about 5,000 meters (16,000 feet) from the entrance. It reached
29.5 degrees (86 degrees F.) in the last 500 meters (1,600 feet) of
the central part. The workmen were then about 1,600 meters (5,100
feet) below the Alpine summit, whose mean temperature is 3 degrees
below zero (27 degrees F.) Thus there was a difference of 32.5
degrees: that is, one "geothermic" degree corresponded to about 50
meters.
This elevation of temperature was not at first regarded with anxiety.
Soon a draught would be produced and would ameliorate the situation.
It was time, for the disease known as "miner's anæmia" had begun to
claim its victims.
The situation at St. Gothard was much more serious. As at Mont Cenis,
a temperature of 29 degrees C. (85 degrees F.) was found about 5,000
meters from the portals of the tunnel. But there remained yet 5,000
meters of rock to pierce. In the center of the tunnel there was
observed for several days a temperature of 35 degrees (95 degrees F.)
Generally it did not vary much from 32.5 degrees (90.5 degrees F.), a
sufficiently high degree, if we remember that the men's perspiration
was transformed into water vapor, and that the air was nearly
saturated with humidity. In these conditions work was very difficult,
and the horses employed to remove the debris almost all succumbed.
Man can bear more than animals. In an absolutely dry air he can endure
a temperature of 50 degrees (122 degrees F.) But in an atmosphere
saturated with water, underground, where the breath of the workmen
fills the narrow space with poisonous vapors, a temperature of even 30
degrees (86 degrees F.) entails serious consequences. In a large
number of workmen the bodily heat rose to 40 degrees (104 degrees F.)
and the pulse to 140 and even 150 a minute. The most robust were
obliged to lay off one day out of three, and even the working day was
itself reduced to five hours, instead of seven or eight.
According to Dr. Giaconni, who for ten years attended the workmen at
Mont Cenis and St. Gothard, the proportion of invalids was as large as
60 to the 100.
More strange yet, the report of the physicians who dwelt at the works
notes the presence among the workmen of the intestinal parasites
called "ankylostomes," which have been observed in Egypt and other
tropical countries, and which are the cause of what scientists call
"Egyptian chlorosis" or "intertropical hyperæmia." This pathologic
state is observed only in the hottest regions of the earth. The victim
becomes thin, pale and dark. He is bathed in continual sweat, devoured
by inextinguishable thirst, and the prey of continual fever. And thus,
adds Mr. Lentherie, "the most robust mountaineer had only to pass a
few months in the depths of the Alps to contract the germs of a
tropical disease. Under the thick layer of snow and ice that enveloped
him he had to work naked like a tropical negro or an Indian stoker on
a Red Sea steamer; and in this Alpine world, where everything outside
reminds one of the polar climate, he sweltered as in a caldron and
often died of heat."
The bad conditions found at St. Gothard will be met also, very
probably, in the new Alpine tunnels that have been projected in recent
years--those at the Simplon, St. Bernard and Mont Blanc. It can be
predicted that for Mont Blanc in particular the temperature of 40
degrees (104 degrees F.) will be far exceeded. M. de Lapparent even
considers that the figure of 55 degrees (131 degrees F.) proposed by
some geologists is moderate, and errs by defect rather than by excess.
The engineer Stockalpa, who for four years has directed one of the
workshops at St. Gothard, and has made a profound study of this
temperature question, does not hesitate to say that under Mont Blanc
the temperature will be 33 degrees (91 degrees F.) at three kilometers
from the entrance, that it will reach 50 degrees (122 degrees F.)
under the Saussure Pass, and 53.5 degrees (128 degrees F.) under the
Tacul Peak, falling again to 31 degrees (88 degrees F.) under the
White Valley.
These are only probabilities, but they are founded on facts, and we
may imagine all the preventive measures that they will render
imperative.
The experience that has been acquired in these latter years has
indicated the best methods of ventilation and cooling. The compressed
air used in the workings produces by its escape a very sensible
lowering of the temperature, which can be made still lower by using
saline solutions whose freezing point is as low as -20 degrees (4
degrees F.), and which will circulate through pipes along the tunnel.
The removal of the debris can be effected by electric locomotives;
thus the horses, which use up the precious air, can be done away
with. The electric light, which can be operated without contamination
or consuming the air, will also render great service; these
improvements can all be carried out with ease. Together with the
preceding, they will form a group of processes that will enable us to
gain the victory over the interior heat of the great Alpine tunnels.
* * * * *