HIS PREDECESSORS 67 



These were all born about the time of Hales' zenith, nor did 

 he live 1 to see the great results they accomplished. But it 

 should not be forgotten that Hales' chemical work made more 

 easy the triumphant road they trod. 



I have spoken of Hales in relation to chemists and physicists 

 because, though essentially a physiologist, he seems to me to 

 have been a chemist and physicist who turned his knowledge to 

 the study of life, rather than a physiologist who had some 

 chemical knowledge. 



Whewell points out in his History of the Inductive Sciences' 2 " 

 that the Physiologist asks questions of Nature in a sense 

 differing from that of the Physicist. The Why? of the Physicist 

 meant Through what causes? that of the Physiologist To 

 what end ? This distinction no longer holds good, and if it is 

 to be applied to Hales it is a test which shows him to be a 

 physicist. For, as Sachs shows, though Hales was necessarily a 

 teleologist in the theological sense, he always asked for purely 

 mechanical explanations. He was the most unvitalistic of 

 physiologists, and I think his explanations suffered from this 

 cause. For instance, he seems to have held that to compare 

 the effect of heat on a growing root to the action of the same 

 cause on a thermometer 3 was a quite satisfactory proceeding. 

 And there are many other passages in Vegetable Staticks 

 where one feels that his speculations are too heavy for his 

 knowledge. 



Something must be said of Hales' relation to his prede- 

 cessors and successors in Botanical work. The most striking 

 of his immediate predecessors were Malpighi 1628 1694, Grew 

 1628 1711, Ray 1627 1705, and Mariotte (birth unknown, 

 died 1684) ; and of these the three first were born one hundred 

 years before the publication of Vegetable Staticks. Malpighi and 

 Grew were essentially plant-anatomists, though both dealt in 

 physiological speculations. Their works were known to Hales, 

 but they do not seem to have influenced him. 



1 Black's discovery of CO 2 , however, was published in 1754, seven years before 

 Hales died, but Priestley's, Cavendish's and Lavoisier's work on O and H was later. 



2 1837, in. p. 389. 



3 Vegetable Staticks, p. 346. 



52 



