1901.] 



and Melting Points to Atomic Mass. 



25 



light on the fundamental causes of the properties of matter. The 

 method will also he applicable to the study of compounds. 



Three diagrams have been drawn and studied. They were drawn as 

 follows : — 



Abscissae. 



Ordinates. 



(a) Densities. 



(b) Melting points. 



(c) Densities and melting points of the elements whose 



spectra have been studied by this method. 



Atomic masses. 



Squares of the 

 atomic masses. 



Diagrams (a) and (b). — The positions of similar elements on these 

 diagrams may be connected by lines which resemble in form those 

 which connect the spectra. In some groups the breaks in the lines 

 are less marked, while in others they are more marked than in the 

 spectra. 



The changes in the diagram involving density are more regular than 

 the changes in those involving melting points. In both of the first two 

 ■diagrams lithium, beryllium, boron, and carbon lie on lines which are 

 nearly straight. 



The Metals of the Alkalies. — There is a decided break in the density 

 diagram between sodium and potassium. A single smooth curve can 

 be drawn through the five metals on the melting point diagram : its 

 form and direction would be similar to those of the line joining the 

 ends of the series in the diagram of spectra, Plate 1, of these elements. 



Copper, Silver, and Gold. — Both the curves joining these metals are 

 remarkable. The connection between the densities of sodium and 

 copper is quite in agreement with those between magnesium and zinc, 

 aluminium and gallium, &c. The angles which the successive lines 

 make with the horizontal increase from the sodium-copper line to the 

 silicon-germanium line. 



There is thus an interesting double connection from sodium to potas- 

 sium on the one hand, and to copper on the other. 



Beryllium, Magnesium, Zinc, Cadmium, and Mercury. — The connections 

 drawn between these are regular ; from magnesium upwards the two 

 curves are approximately symmetrical. 



Beryllium, Magnesium, Calcium, Strontium, and Barium. — The connect- 

 ing lines are only slightly curved. The melting points of strontium 

 and barium are not known accurately : those recorded place them on a 

 slightly curved line which passes on to beryllium. 



The double connection from magnesium to calcium and to zinc is 

 •another interesting feature. 



Boron, Aluminium, Gallium, Indium, and Thallium. — There is a break 



