52 MORRIS LOEB 



nature of substances as we see them around us, had many 

 vague notions as to the causes from which the various proper- 

 ties of the substances might arise. One might almost say that 

 the various Greek philosophers devised every conceivable 

 notion as to the origin of matter which a sensible man could 

 happen upon. Among these there were two which must claim 

 our attention, because they throw much light upon the differ- 

 ing hypotheses about physical phenomena up to the present 

 day. One notion was that every substance is made up of cer- 

 tain ingredients whose presence caused it to have its own par- 

 ticular properties, which were really the properties of the in- 

 gredients. Aristotle called these ingredients elements, and 

 he mentioned as such elements, fire, air, earth and water, of 

 which he considered earth as that which was cold and dry, 

 water that which was cold and moist, fire that which was hot 

 and dry, and air that which was hot and moist. More elements 

 were added during the Middle Ages, so that the ancient al- 

 chemist spoke of six or seven different elements out of which 

 all known substances were imagined to be composed. Now, 

 since gold, silver and lead, for instance, are all composed of 

 the same Aristotelian elements, it seemed natural that if one 

 changed the proportion of these elements, lead, for instance, 

 might be converted into silver or gold. 



To the present time we have retained the word element, but 

 we have given to it a somewhat altered meaning, because we 

 have recognized that some of the substances thought by the 

 ancient and mediaeval philosophers to be simple are really com- 

 pounds or mixtures; while many of the substances which they 

 considered composite baffle the skill of the chemist when he 

 attempts to disintegrate them. The simple metals are now all 

 of them considered as chemical elements; and we were until 

 very recently apt to look back with a good deal of scorn upon 

 the alchemists who strove to change one metal into another. 



