26 ESSAYS BIOGRAPHICAL AND CHEMICAL 



differed from that obtained by submitting bones to the 

 same process. He clinched his point by distilling the 

 distillates themselves in turn in fact by performing what 

 we now call a ' fractional distillation ' and showed that 

 it was possible to divide them in turn into several liquids, 

 differing from each other in properties. In this he antici- 

 pated a process now practised on a very large scale, namely 

 the manufacture of vinegar from wood, which he success- 

 fully separated from wood-spirit and tar. 



Almost all research, before Boyle's time, employed two 

 processes, ignition or heating in contact with air, and dis- 

 tillation, or heating in a vessel of irregular shape, named 

 an alembic, leading the vapours through a cooled tube, 

 still called a worm, and collecting the liquefied product in 

 a pear-shaped vessel, named a receiver. Heat was assumed 

 to be the universal resolver of bodies ; and the products 

 of the action of heat on compounds were accepted as 

 elements. Boyle doubted this; he questioned whether 

 the products obtained on distillation were pre-existent in 

 the substances distilled, as the theory of elements would 

 require. He found that on distillation the same substances 

 are not always produced, nor the same number ; and he 

 demonstrated that these products themselves are not pure 

 or elementary bodies, but ' mixts.' He says : ' It is to be 

 doubted whether or no there be any determinate number 

 of elements, or if you please, whether all compound bodies 

 do consist of the same number of elementary principles 

 or ingredients.' 



But Boyle was not merely a destroyer ; he also, if not 

 in so orderly a manner, attempted to construct a theory 

 of his own. He appears to have held the notion of a 

 universal matter, and to have conceived the different 

 varieties to be due, not to the presence of separable pro- 

 perties, but to the form and motion of its minute portions. 

 In supporting this doctrine against the theories prevalent 



