548 



SCIENCE 



[N. S. Vol. XXXIV. No. 878 



of things? These questions may never be 

 adequately answered, but science must 

 ceaselessly endeavor to solve the problem 

 which they present. 



A first step is clearly to find the way in 

 which each property varies in relation to 

 every other. With this in mind, let us 

 appeal to the irregular system of the peri- 

 odic classification, which formed the sub- 

 ject of the Faraday lecture by Mendeleeff 



The device is not new. Carnelley compared 

 Lothar Meyer's atomic volume curve with 

 that of melting points, and other similar 

 data have been plotted ; but the method has 

 not been used to its full extent. 



Let us then turn to the diagram (Fig. 3) 

 in which the variations in a number of 

 properties are plotted with relation to the 

 atomic weights. Prominent among the 

 lines is the atomic-volume curve just men- 



ICOMPARISOIS of HEATSf, 

 |\ OF FORMATION of 



OXIDES 



N 1001 



•■ v.. f^^. I 



twenty-two years ago. This mysterious 

 index of uncharted tendencies must hide 

 within itself guiding ideas capable of 

 pointing us onward. 



Clearly each property must receive, not 

 merely qualitative, but strictly quantitative 

 treatment. With this in mind, let us com- 

 pare our various facts by plotting atomic 

 weight in one direction, and all the other 

 properties in another. Then by noting the 

 parallelism or anti-parallelism of the wavy 

 lines, many relationships may be traced. 



tioned. Below it is plotted the almost 

 parallel line depicting the compressibilities 

 of the solid elements as determined at Har- 

 vard ; these are immediately seen to be, like 

 the atomic volumes, periodic functions of 

 the atomic weights. The parallelism can 

 not but suggest that atomic volume and 

 compressibility are fundamentally con- 

 nected; and, indeed, the theory of com- 

 pressible atoms gives a plausible explana- 

 tion of the connection. We should expect 

 the large atomic volumes to be more com- 



