plants; but we are compensated for this by his making us acquainted with everything fundamentally important and new which could at that time be said on the chemistry of the food of plants. Speaking of the 'elements' or 'principles' of plants, Mariotte propounds three hypotheses. The first is, that there are many immediate principles (principes grossiers et visibles, evidently what we should call proximate constituents) in plants, such as water, sulphur or oil, common salt, nitre, volatile salt or ammonia, certain earths, etc. ; and that each of these immediate constituents is a compound of three or four more simple principles, which have united together into one body; nitre for instance has its 'phlegma ' or tasteless water, its 'spiritus,' its fixed salt, and other things; common salt in the same way has the like constituents, and it may be assumed with much probability, that these more simple principles also are compounds of parts that differ among themselves, but are too small to be distinguished by any artificial means as to figure or any other characters. Having shown how certain principles unite together, he goes on to say, that he is unwilling to ascribe to them any sort of consciousness (connaissance) by which they seek to unite together ; but he thinks that they are endowed with a natural disposition to move towards one another, and to unite closely as soon as they touch one another ; though it is very difficult to define the nature of this disposition, it is enough to know that there are many instances of such movements to be found in nature ; thus heavy bodies move towards the centre of the earth, and iron to the magnet ; nor are these movements more difficult to conceive, than that of the planets in their courses or of the sun round its axis, or that of the heart in a living animal. With this first hypothesis Mariotte places himself, in opposition to the Aristotelian doctrine with its entelechies and final causes which prevailed at that time among botanists and physiologists, upon the firm ground of modern science with its atoms, and its assumption of necessarily active forces of attraction.
