PRINCIPLES UNDERLYING METAMORPHIC PROCESSES 503 
wherein Q is the heat (absorbed) of melting in calories per gram, and 
V; and V, the respective volumes of 1 gram of substance at the 
melting-point in the liquid and the solid state. An example of the 
agreement between calculation from this formula and actual obser- 
vation of the effect of pressure on the melting-points of tin, bismuth, 
cadmium, and lead is afforded by the following table, taken from a 
former paper from this laboratory;' the divergences are such as are 
to be expected in view of the present uncertainty in the values of 
Q, the latent heat of melting: 
TABLE I 
EFFECT OF UNIFORM PRESSURE ON THE MELTING-PoINTS OF CERTAIN METALS 
Latent Heat Jol. Chan A ,000 : 
Metal cal. per gram by Meine i ale nes eae aT Yas sate Bony 
Q Vi-V; tion II DOBEEYe 
SS 5 Gromer TAR 5 0.003894 +3.45 +3.28 
Cdk nes: EO 0.00564 +6.10 +6.29 
1a Gono oy 0.003076 +8.59 +8.03 
Bee tea c1o 12.6 —0.00342 —3.67 —3.55 
Equation II enables us therefore to calculate the effect of uni- 
form pressure on melting-point if certain physical constants of the 
material are known; unfortunately, however, these constants are 
known for very few substances, among which are practically none 
of direct geologic interest. 
Direct determinations of the effect of pressure on melting- 
point have been made only as follows: potassium,? sodium,3 
mercury,’ water,’ and a large number of organic substances® (e.g., 
benzol, phenol, naphthalene, etc.) including several substances 
capable of existence as a liquid-crystalline phase.? All of these 
t Johnston and Adams, Am. Jour. Sci., XXXI (1911), 516; Z. anorg. Chem., 
LXXII (1911), 29. 
2?Tammann, Krystallisieren und Schmelzen. 3 Ibid. 
4P. W. Bridgman, Proc. Am. Acad., XLVII (1912), 349; Z. anorg. Chem., 
LXXVII (1912), 377. 
5 Proc. Am. Acad., XLVII (1912), 441. 
6Tammann, Joc. cit.; Hulett, Z. physik. Chem., XXVIII (1899), 629 (pressures 
only up to 300 atm.). 
7 Hulett, loc. cit.; Korber, Z. physik. Chem., LUXXXII (1913), 45. 
