MODERN SCIENCE. 191 



historical vision to dismiss their names with a shrug of the 

 shoulders, as some have done during the Revival and since.. 

 The only chemist we remember who might have won the 

 approbation of these hypercritics was Stahl, who, last century, 

 waylaid many chemists by his Phlogistic theory until it was 

 at last exploded by the discoveries of Lavoisier. They would 

 no doubt have admired a theory which was wholly imaginary, 

 from the very fact that it displayed ingenuity without verifi- 

 cation, and that it was in accord with their own way of settling 

 difficulties by what they considered an effort of genius without 

 study. Stahl's theory of combustion furnishes a sound analogy 

 to the SPIRIT THEORY of earlier days, with this enormous dif- 

 ference, however, that whereas Phlogiston affected only a set 

 of phenomena and arrested one branch of science only, the 

 doctrine of spirits affected phenomena universally, and would 

 have blocked the way to every branch of science. Fortunately 

 the scientific method prevailed, and science did wonders 

 "undreamt-of by Baconian philosophy." We need hardly 

 point out that chemistry descends from alchemy through 

 Paracelsus, Libavius, Van Helmont, and partly Gilbert the 

 transition being fairly steady after Paracelsus had taught the 

 science in public, although modern chemistry cannot be said 

 to have been in existence until the discovery of oxygen. 



We now come to a series of branches which are so bound 

 together that they should be treated abreast of one another, 

 namely, mathematics, astronomy, physics, and mechanics. 

 But we must be content with taking them separately. It 

 will be easy for the reader to see their connection as we 

 proceed. 



GROUP IV. MATHEMATICS. 



1596 1650. Descartes found the method of determining 

 the tangents of curves ; APPLIED ALGEBRA TO THE GEO- 

 METRY of curves. " He showed," says an excellent master of 

 the subject,* " that every equation may be represented by a 

 curve, or figure in space, and that every bend, point, cusp, 



* Mr. Jevons. 



