CHAP. II.] of Plants. Mariotte. 463 



Marietta's second hypothesis more specially concerns the 

 chemical nature of plants; he supposes that several of his 

 principes grossiers are contained in every plant, and he endea- 

 vours first to explain their source ; the motes in the air, he 

 says, which when burnt by lightning smell of sulphur, are 

 carried by rain into the earth, and parts of them are taken up 

 into the plant. Moreover distillation in all plants produces a 

 water, which the chemists call phlegma, and also acids and 

 ammonia, and if the residuum is burnt there remains an ash, 

 from which we obtain an earth which is without taste and 

 insoluble in water, and fixed salts ; these salts differ from one 

 another according as they are mixed with more or less acid and 

 ammoniacal spirit or other unknown principles, which the fire 

 could not volatilise. It is not to be wondered at that these 

 principles are found in plants, since they derive their food from 

 the earth which contains them. We see how great has been 

 the advance since the time when Van Helmont believed that he 

 had proved by his experiment, that all the materials in plants 

 come from pure water. 



It remained to confront one view of the source of the 

 substances in plants, which was also drawn from the treasure- 

 house of Aristotelian conceptions, and was still in vogue. It was 

 supposed that the very materials of which the plant is composed 

 were contained in their own form in the earth, and had only 

 to be taken up by the roots. Aristotle had himself said : ' Every- 

 thing feeds on that of which it consists, and everything feeds 

 on more than one thing; whatever appears to feed only on 

 one thing, as the plant on water, feeds on more than one thing, 

 for earth in the case of the plant is mixed with the water ; 

 therefore the country-people water plants with mixtures of 

 things.' This passage might leave some doubt about Aristotle's 

 view, if we did not find the following : ' As many savours as 

 there are in the rinds of fruits, so many it is plain prevail also 

 in the earth. Therefore also many of the old philosophers 

 said, that the water is of as many kinds as the ground through 



