CunnincHam—Crystallization of Minerals in Iyneous Rocks. 887 
M. W. Spring’ in the case of certain metallic alloys. Both of these 
criteria when plotted as curves to a suitable scale exhibit in 
general pretty much the same characters. ‘Thus, if in the ac- 
companying curves, figs. 1 to 4, we represent temperatures by 
abscissee, and volumes by ordinates, then the slope of the curve at 
any point represents the coefficient of expansion (a) at that 
l 
do 
temperature. Atthe melting point (MP) we have a sudden ex- 
pansion while the temperature remains constant. The passage 
M.P. Temperature 
Fig. 4. 
wy 
M. P. Temperature O Temperature 
Fics. 1-4.—Curves showing the connexion between Temperature and Physical 
Properties in passing from Solid to Liquid. 
from solid to liquid may be sudden which would be indicated by 
sharp corners at B and C (fig. 1), or it may be more or less gradual, 
indicated by one or both corners being rounded (figs. 2 and 38). 
The vertical height BC represents the volume change on passing 
from solid to liquid which is usually an expansion as in the 
1M. W. Spring, Bull. Acad. R. des Sciences, des Lettres, et des Beaux-Arts de 
Belgique, 2° Séries, T. xxx1x. (1875), p. 648. 
