3 A N:o 16) ” Melting and boiling point of minerals II. 11 
value. The actual boiling point of carbonic acid is at 30 at- 
— mospheres 24 9 below the calculated boiling point, whereas 
— othe boiling point of oxygen exceeds at 30 atmospheres the 
i calculated temperature by 19 94. All the remaining sub 
— stances show much smaller differences between the meéea- 
k sured boiling points and:the calculated values. — At 90 
— atmospheres the difference between the calculated and the 
observed boiling temperatures of water is 35 960 of the dif- 
ference in temperature degrees between the boiling point 
at I atmosphere and the boiling point at 90 atmospheres. Asa 
rule the differences between the calculated and the observed 
boiling point at 90 atmospheres, expressed in percent of the 
total change in temperature, is smaller than at 10 or at 30 
atmospheres. If the behaviour of water is considered to 
be an anomaly as is also the temperature variation of 
several other physical constants of this fluid one seems 
entitled to say that the simpler formula of Ramsay and 
Young holds true within a margin of less ihan 15 9 of 
-ihe change of the boiling points. 
Thus, although Ramsay's and Young's rule of the con- 
stant ratios of the boiling points of fluids under: different 
pressures is not able to render any precise values, it mav 
give an approximate estimation of the temperature at 
which different fluids, the boiling points of which are known 
only at low pressures, may be brought to boil under another 
and much higher pressure. Table IV contains the boiling 
points of some substances, which are of geological interest. 
It may be mentioned that a watercolumn 940 meters 
high gives a pressure of 90 atmospheres. If accordingly a 
point at a depth of 940 meters, or we shall say 1000 meters 
below the surface of the earth, is under the hydraulic pressure 
of the water in fissures and cracks in the crust of the earth, 
it stands under a pressure of about 90 atmospheres. — If 
on the other hand the pressure in the point to be considered 
represents the weight of a layer of molten silicate magma or 
a molten magma and solidified rock swimming on top of the 
same, the depth at which the previously mentioned pres- 
sures may be encountered is 2,5 times smaller than the numbers 
