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THE POPULAR SCIENCE MONTHLY 



heard a rumbling sound and felt a quaking 

 of the earth, which they took to be a veri- 

 table earthquake. But, as the sound was not 

 repeated, they soon forgot the occurrence, 

 and continued their chase till they came to 

 the vicinity of the Bear Tooth. What was 

 their surprise to find that the stupendous 

 mass of the eastern tusk had been dislodged, 

 sweeping for a quarter of a mile through a 

 forest of heavy timber, and overwhelming 

 with its debris the ground round about ! 

 Virginia City, in the same State, is gradually 

 slipping down the mountain-side on which 

 it is built. The movement is gradual, and 

 imperceptible at the surface. A water-main 

 recently uncovered was found telescoped for 

 the space of one foot, and otherwise injured. 

 A fissure has been traced in the ground on 

 the western side of the town ; on one side 

 of this the ground is three feet higher than 

 on the other. 



The Death of a Generation. A writer 

 in an English magazine studies from birth 

 to death the march of an English genera- 

 tion through life, basing his remarks on the 

 annual report of the registrar-general. The 

 author singles out, in imagination, a genera- 

 tion of one million souls, and finds that of 

 these more than one-fourth die before they 

 reach five years of age. During the next 

 five years the deaths number less than one- 

 seventh of those in the first quinquennium. 

 From ten to fifteen, the average mortality is 

 lower than at any other period. From fifteen 

 to twenty the number of deaths increases 

 again, especially among women. At this pe- 

 riod, the influence of dangerous occupations 

 begins to be seen in the death-rate. Fully 

 eight times as many men as women die vio- 

 lent deaths. The number of such deaths 

 continues to rise from twenty to twenty-five, 

 and keeps high for at least twenty years. 

 Consumption is prevalent and fatal from 

 twenty to forty-five, and is responsible for 

 nearly half the deaths. From thirty-five to 

 forty-five the effects of wear and tear begin 

 to appear, and many persons succumb to dis- 

 eases of the important internal organs. By 

 fifty-five the imagined million has dwindled 

 down to less than one-half, or 421,115. Af- 

 ter this, the death-rate increases more rap- 

 idly. At seventy-five, there remain 161,124, 

 and at eighty-five, 38,565. Only 202 reach 



the age of one hundred. At fifty-three, the 

 number of men and women surviving is 

 about equal, but from fifty-five onward the 

 women exceed the men. 



Setting Tires with Hot Water. The use 



of hot water in place of fire for expanding 

 tires may not be new, but it is less common 

 than it ought to be, if we are to accept as 

 accurate the results said to be obtained in 

 the workshops of the Moscow-Nizhni Rail- 

 road, in Russia. There an iron tank, one- 

 fourth filled with water, is fixed near a sta- 

 tionary boiler, from which a steam-pipe is 

 led through it, capable of heating the water 

 to 212 Fahr. Into this the tire is plunged 

 by means of a portable crane, and, after an 

 immersion of from ten to fifteen minutes, is 

 taken out and immediately placed on the 

 wheel. The allowance for shrinking in 

 other words, the difference between the 

 diameter of the skeleton and that of the 

 tire is 0.75 millimetre to a metre. This is 

 ascertained by gauges of great accuracy ; 

 and, if it be deviated from, the tire will 

 either be loose after cooling, or too small 

 to get on the wheel. When fire is used, 

 the tire can never be heated equally or 

 cooled equally in all parts, and, in conse- 

 quence, is sure to be more or less oval in 

 form, which is not the case when hot water 

 is employed. The officials of the railroad 

 named above made a comparison of the two 

 methods, from which it appears that, during 

 a six years' trial of fire-shrunken tires, 37 

 per cent, ran loose, and 5 per cent, were 

 broken ; while, during a three years' trial 

 of water-shrunken tires, less than one per 

 cent, ran loose, and only a single tire was 

 broken. 



Distribntion of Prairie and Forest. 



Many are the theories which have been 

 offered to explain the distribution of prairie 

 and forest. The continued existence of the 

 prairies of the West has been attributed to 

 the annual fires ; to the nature of the soil 

 and its underlying rock; to deficiency of 

 rainfall ; finally, to deficiency of winter rains 

 and snow. The contrary conditions would, 

 according to these theories, favor the pro- 

 duction of forests. Prof. J. E. Todd, who, 

 in the American Naturalist, discusses this 

 problem with special reference to South- 



