Meteorlteii and What they Teach us. — Ilensnldt. 70 
this temperature carbonic acid can not exist in its liciuid con- 
dition, however great the pressure may be to which it is 
exposed. This is in accordance with an interesting law the 
existence of which has been proved beyond any doubt by 
recent investigation. After certain temperatures are reached 
liquids enter into the gaseous state, no matter what the pres- 
sure may be. The temperature under which a certain liquid 
is no longer able to retain its characteristic features, but 
transforms itself into a gas, has been called by Prof. Andrews, 
of Belfast, its "critical point" and from experiments made by 
him it has been convincingly shown that it is not possible to 
maintain the liquid condition of CO,- at any temperature 
beyond 30°92'C. In all the cavities contained in these 
meteoric sections which have come under the writer's obser- 
vation the bubbles suddenl}' vanished at a temperature of 
from 30° to 31° C, sometimes even exhibiting that peculiar 
phenomenon of ebullition to which Mr. Noel Hartley, more 
than ten years ago, already drew attention. Now if the 
enclosed fluids had been water the bubbles would not have 
shown the least indication of a change at this temperature. 
The writer heated a section of quartz, the cavities in which he 
knew to contain water, to the boiling point without detecting 
the smallest effect on the bubbles. 
Among the many chemical tests which have been resorted to 
in order to determine the presence of carbonic acid in mineral 
cavities we will only mention that of Vogelsang and Geissler, 
of Bonn, who crushed rock-crystals in which cavities occurred 
which they suspected to contain liquified CO.., under baryta 
water, and observed that the latter became turbid, owing to 
the formation of carbonate of baryta. 
Now, taking for granted that the fluid material contained in 
the cavities of these meteorites, is really carbonic acid, which 
we may safely do, as it presents no points of analogy to any 
other known substance, and that the bul.ibles, which move bo 
restlessly about in their tiny prisons are the same substance 
in its gaseous condition ; what do these facts teach us respect- 
ing the circumstances under which the meteoric masses were 
originally formed? 
Carbonic acid is a gas which can only be reduced to the 
condition of a liquid by extreme pressure. It requires a pres- 
sure of no less than G5 atmospheres to condense CO... which is 
