established in the estimation of philosophers than that em- 

 bodied in the assertion: "Nature abhors a vacuum;" and 

 when in 1590 the well-sinkers of the Grand Duke of Florence 

 found their pumps would not lift the water out of a well 

 forty feet deep, Galileo was applied to for explanation of the 

 difficulty and for a remedy. The great man is said to have 

 informed the workmen that nature's abhorrence of a vacuum 

 did not extend beyond thirty -three feet ! Galileo himself being 

 unable to assign the true reason, which was afterwards 

 determined by his famous pupil Torricelli. 



In the last year of the sixteenth century an English phy- 

 sician, Dr. William Gilbert, published a book that laid the 

 firm foundations of a new branch of physics, electricity. The 

 familiar behavior of a magnet in attracting particles of iron, 

 and of amber in drawing to itself bits of paper and light 

 articles, had been known to the ancients, but Dr. Gilbert made 

 a thorough experimental study of these and related pheno- 

 mena, discovering that glass, resins and certain precious 

 stones had the same property as amber. He also demon- 

 strated the laws of magnetic polarity and the uses of arma- 

 tures; and while he deduced no general law he announced 

 the theory that the earth itself is a great magnet. This 

 grand monograph worked prodigies in removing from mag- 

 netic phenomena the superstitions clustering around them. 



Pliny's Natural History, written in the first century, 

 remained the unquestioned authority on all matters pertain- 

 ing to plants, animals and minerals for more than thirteen 

 hundred years, and was responsible for a mass of extra- 

 ordinary superstitions, many of which lingered as "vulgar 

 errors" until very recent times. Pliny transcribed from all 

 known writers on natural history the most absurd tales and 

 made no effort to examine their authenticity; he peopled the 

 water, land and air with fabulous creatures having wonder- 



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