THE BREATH OF LIFE 



high temperature away from the air, and its molecu- 

 lar structure seems to change, and we have the red 

 variety, which is tasteless, odorless, and non-poison- 

 ous, and is not affected by contact with the air. 

 Such is the mystery of chemical change. 



rv 



Science has developed methods and implements 

 of incredible delicacy. Its " microbalance " can es- 

 timate "the difference of weight of the order of the 

 millionth of a milligram." Light travels at the 

 speed of 186,000 miles a second, yet science can 

 follow it with its methods, and finds that it trav- 

 els faster with the current of running water than 

 against it. Science has perfected a thermal instru- 

 ment by which it can detect the heat of a lighted 

 candle six miles away, and the warmth of the hu- 

 man face several miles distant. It has devised a 

 method by which it can count the particles in the 

 alpha rays of radium that move at a velocity of 

 twenty thousand kilometers a second, and a method 

 by which, through the use of a screen of zinc-sul- 

 phide, it can see the flashes produced by the alpha 

 atoms when they strike this screen. It weighs and 

 counts and calculates the motions of particles of 

 matter so infinitely small that only the imagination 

 can grasp them. Its theories require it to treat the 

 ultimate particles into which it resolves matter, and 

 which are so small that they are no longer divisible, 

 60 



