566 



POPULATION OF THE 

 UNITED STATES 



TOTAL COAL MINED IN THE 

 UNITED STATES PRIOR TO IQlj 



913 PRODUCTION 



come on. Eacn li^nt remains on only a 

 fraction of a second. The whole effect is 

 that of a giant swinging a large red lantern. 

 So effective is the lighting 

 system that in the year 

 since the barrier gate was 

 installed not a single acci- 

 dent has occurred. On other 

 bridges not thus equipped 

 the gates are out of com- 

 mission much of the time 

 owing to the fact that auto- 

 mobiles run into the gate 

 arms. 



Recently a trial test was 

 deliberately made with a 

 street car running ten miles 

 an hour. At that speed the 

 car had a striking weight of 

 fifty - three thousand - foot 

 pounds. The street car was 

 brought to a complete stop 

 in fifteen feet. The car was 

 not damaged in the least, 

 and the motorman, who re- 

 mained at his post, was not 

 even severely 

 shaken up. 

 The barrier 

 gate was also 

 undamaged. 



The yield- 

 ing chain bar- 

 rier for rail- 

 road crossings 

 and for bridge 

 approaches 

 frequented 

 by light traf- 

 fic, consists of 

 two uprights 

 or structural 

 steel posts, 

 one at each 

 side of the 

 roadway, 

 connected at 

 the top with 

 a steel truss. 

 The weight of 

 the barrier is 

 counterbal- 

 anced by 

 means of a 

 counterweight contained within the two 

 side posts. When struck by a vehicle the 

 barrier gives, the chains paying cut, and 

 gradually absorbing the energy of the shock 

 until it brings the vehicle to a stop. 



Popular Science Monthly 



We Burn Coal Lavishly, But We Have 

 Plenty of It to Burn 



WE 



COAL RESERVE 



IN THE 

 UNITED STATES 



The coal mined in this 

 country up to 1913 and 

 what we still have on hand 



POPULATION OF THE WORLD 

 OUTSIDE OF THE 

 UNITED STATES 



TOTAL COAL MINED IN THE WORLD 



OUTSIDE OF THE UNITED STATES 



PRIOR TO 1913 \ 



1913 

 PRODUCTION 



COAL RESERVE 



•IN THE 

 WORLD OUTSIDE 



OF THE 

 UNITED STATES 



Comparison between the world's population 

 and coal reserve. We have used less than 

 one-half of one per cent, of the total quantity 



HILE it is true that the 

 nited States is the largest 

 consumer of coal in 

 the world , using 

 nearly forty per cent 

 of the world's total 

 production, it is 

 something of 

 a comfort to 

 know that we 

 have not yet 

 consumed 

 more than one-half of one 

 per cent of the total quan- 

 tity which geologists esti- 

 mate is at present contained 

 within our borders. 



The annual production of 

 coal in the United States 

 has increased more than 

 eight hundred per cent in 

 thirty-five years — from 

 sixty-eight million tons in 

 1879 to more than a half 

 billion tons in 1913. Not- 

 withstanding the enormous 

 amount of coal available, 

 our exports in 1913 

 amounted to very little, 

 only about four per cent of 

 the entire output. In this 

 year Great Britain ranked 

 second as a coal producer. 

 Coal was first worked in 

 the United States in Rich- 

 mond, Virginia, in the mid- 

 dle of the eighteenth cen- 

 tury, and indeed that State 

 in proportion to its size, 

 long surpassed all the others 

 in varieties of coal pro- 

 duced, and area of coal 

 measures, though there it 

 had the disadvantage that 

 the coal was generally 

 deeply buried. In 1820 the 

 total output of coal in the 

 country was three thousand 

 four hundred and fifty tons; 

 by 1850 the annual output 

 was over seven million tons. 

 According to the United States Geologi- 

 cal Survey the total area of coal-beds is 

 close to five hundred thousand square miles, 

 of which about one-half contain anthracite 

 and bituminous coal. 



