46 THE REALITIES OF MODERN SCIENCE 



An illustration is their reasoning as to the speed of 

 falling bodies. They had probably noticed that a 

 pebble falls faster than a feather, and they concluded 

 that " bodies fall with velocities proportional to their 

 weights." This conclusion was not tested by observing 

 the fall of two bodies of different weights, but with 

 essentially the same air resistance, until Galileo in 

 1590 actually tried the experiment. From the leaning 

 tower of Pisa, a height of about 180 feet, he dropped 

 balls of different materials and of different sizes. 

 He found that they fell in almost the same times, and 

 that light objects like pieces of paper fell more nearly 

 like heavy balls when the paper was tightly wadded into 

 a ball. Reasoning a posteriori he concluded that except 

 for the resistance of the air all bodies would fall through 

 the same height in the same time. Galileo could not 

 perform the experiment under conditions where air 

 friction and buoyancy were eliminated, for the air pump 

 was not invented until about sixty years later. But 

 since he found that the more nearly the effects of the 

 air on two falling bodies were equalized, the more 

 nearly did they fall through the same height in equal 

 times, he reasoned for the limiting case that the two 

 bodies would fall with equal velocities. 



The importance in science of inductive reasoning 

 was not fully appreciated until even after Galileo's 

 time, although from the time of Roger Bacon there 

 were men who advocated it. With the definitions of 

 these two forms of reasoning in mind we may now see 

 more clearly the method of science. From a mass of 

 correlated information as to some class of natural 

 phenomena, scientists reason inductively to obtain a 



