HEAT IN GREAT TUNNELS. One phase of the construction of tunnels through the Alps was recently discussed by M. Brandicourt, secretary of the Linnaean 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 anaemia" 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.