14 MORRIS LOEB 



Their reasoning appeared to them to be as logical as ours is, 

 when we propose transforming the sap of the pine into the 

 essence of vanilla, or of converting clay into the true ruby. 



As I have said, we recognize upwards of sixty-five elements, 

 but we rarely see any of these pure. Terrestrial objects must, 

 then, be made up of combinations of these elements. In 

 order to study them in the pure state, they must usually be 

 separated from each other; and they are worthy of very care- 

 ful study. 1 . . . 



You are aware of the Periodic Law of Newlands, Lothar 

 Meyer, and Mendeleeff, which traces such remarkable re- 

 lations between the various properties of the elementary 

 substances and the relative masses of their imaginary atoms. 

 Attempts to connect this law with the idea that the elements 

 are compounds in a chemical sense are abortive. I believe 

 that the law can be more readily traced to the relation of the 

 quantities in which our fundamental ideas of matter, energy, 

 and space are associated for each element. The atoms of the 

 elements have undoubtedly different densities. That is to 

 say, our knowledge of the sizes of the atoms, limited though 

 it be, does not allow us to suppose that an oxygen atom occu- 

 pies sixteen times the volume which a hydrogen atom requires, 

 although this is the ratio of the masses of these two kinds of 

 atoms. For the same amount of space there seems to be more 

 matter in the oxygen atom than in the hydrogen atom; we 

 may assume that similar relations exist in other cases with 

 regard to energy and matter. For each element we should have 

 to assume new quantities of matter, space, and energy; and 

 the ratios of every one of the three with respect to each other 

 would vary. We might suppose, however, that for a series 

 of elements the ratio of two of the fundamental quantities 



1 The lecture notes on physical chemistry here became fragmentary. The fol- 

 lowing six pages were taken from two summaries evidently prepared for addresses 

 on other occasions. [EDITOR.] 



