230 HISTORY OF SCIENCE. 



were the gases ; and Van Helmont was also the first who introduced 

 the word gas into science. This word is derived from ga/ist or geist, 

 which signifies spirit. " Charcoal," he says, " and in general those 

 bodies which are not immediately resolved into water, disengage by 

 combustion spiritum sylvestrem. From 62 Ibs. of oak charcoal i Ib. 

 of ash is obtained, therefore the remaining 61 Ibs. are this spiritus 

 sylvestris. This spirit, unknown hitherto, I call by the new name of 

 gas. It cannot be enclosed in vessels, or reduced to a visible condi- 

 tion. There are bodies which contain this spirit and resolve them- 

 selves entirely into it : in these it exists in a fixed or solidified form, 

 from which it is expelled by fermentation, as we observe in wine, 

 bread, etc." This passage is remarkable, not only for the explicit 

 mention of carbonic acid gas (as we now call it) as a product of fer- 

 mentation, and for the introduction of the word gas for the first time, 

 but also for the appeal to the balance, the instrument that, as we 

 shall presently see, made a complete revolution in chemical science. 

 Van Helmont points out that the gas sylvestre is produced by the 

 action of acids on shells, that it is present in caves and mines, that 

 mineral waters contain it, and that it is engendered in putrefaction, 

 combustion, etc. By "gas sylvestre" Van Helmont designated all gas 

 which resisted his efforts to reduce it into a visible form. Thus he 

 describes carbonic acid, sulphuric acid, and other gases under this 

 name. 



In Van Helmont's writings it is observed that he sometimes uses 

 the word element in the ancient sense ; but he admits ofily air, earth, 

 and water fire is excluded, because it does not form material com- 

 bination with other bodies. Sometimes, on the other hand, he sides 

 with the alchemists in recognizing as the elements of all bodies, salt, 

 sulphur, and mercury. He remarks that in the solution of metal by 

 an acid, the essence of the metal is not destroyed, but it exists in the 

 solution as common salt does in water in which it has been dissolved. 



ROBERT BOYLE (1627 1691) was one of the original founders of 

 the Royal Society, and his labours greatly contributed to the progress 

 of more than one branch of science. His is a noble example of a life 

 devoted to the study of nature in preference to the pursuit of worldly 

 pleasures. He modestly declined to accept even those distinctions to 

 which his position and attainments gave him a just claim. Though 

 the son of an earl, he would not accept a peerage for himself, and he 

 refused the presidentship of the Royal Society when that honour was 

 offered to him. The advantages which birth^nd fortune placed in his 

 hand were employed in promoting science by every possible means. 

 The first scientific work he published appeared at Oxford in 1660 

 under the title of " New Experiments Physico-Mechanical touching 

 the Spring of the Air and its Effects." He describes the successive 

 improvements he effected in the construction of the original air-pump 

 of Guericke. His chief object was to demonstrate the elasticity, or 



