446 THE POPULAR SCIENCE MONTHLY. 



pretty images seen in a reversed telescope, discovered a means ever 

 since universally employed of producing artificial signals which have 

 precisely the same properties as though they stood in infinite dis- 

 tance; or when a Newton made of the spectrum, a thing that had 

 been craped at as a mere curiosity a thousand times before, the 

 foundation of modern optics ? 



The sudden arrival at a truth from all sides a thing so fre- 

 quent in the history of the sciences, which often makes it hard to 

 decide to whom the honor of new discoveries properly belongs of 

 itself shows that cultivated minds in general have grasped the idea. 

 The human race might be compared to a traveler in unexplored 

 countries. As the booty he brings home is rich in proportion to 

 the extent of his own intellectual acquirements, which enable him 

 to distinguish what is new from what is hackneyed, so mankind has 

 need of schooling in order to understand what is of importance in the 

 events occurring round about. In short, one must be impressible in 

 order to be impressed. 



Ever since the fourth century of our era, the Chinese have used 

 the magnetic needle as a nautical instrument, and thus w r ere enabled 

 to extend their voyages as far as India and Eastern Africa. The 

 Arabians brought us into relations w T ith India in the eighth century, 

 and the Crusaders with the Orient in the tenth, and yet the mariner's 

 compass was not introduced into Europe till the twelfth century. 



Does it not seem wellnigh incredible that we cannot trace the use 

 of the free-hanging plummet, as a means of observation, farther back 

 than the period when the Arabians were our teachers in astronomy; 

 nay, that only in the fifteenth century it found general acceptance by 

 the exertions of our renowned countryman Georg von Peuerbach ? 



When, at the beginning of the last century, Amontons worked 

 with entire success an optical telegraph ; and Franklin, fifty years 

 later, robbed the clouds of their lightning ; and when both of these 

 men were dismissed even by a learned body like the Paris Academy 

 with stale witticisms ; if for thousands of years countless aerolites 

 have been seen to fall to the earth without ever giving rise to an 

 inquiry as to the nature of meteors the reason is always to be 

 found in the self-same indisposition to receive what is new, which 

 caused mediaeval Europe to pass by unnoticed the golden teachings 

 of a Roger Bacon or of a Leonardo da Vinci. Both of these stood 

 high above Francis Bacon as inductive philosophers ; but he had 

 for his contemporaries men who had been taught by Copernicus, 

 Galileo, Kepler, and others, some of the mighty consequences of that 

 principle which Francis Bacon had now simply to formulate in order 

 to have it universally accepted. Here and there other eminent men 

 had, long before Roger Bacon himself, hit on the right way of investi- 

 gating Nature. This assertion, too, rests on unquestionable evidence, 

 which, however, is perhaps not so familiar to you. The visibility of 



