42 
ABBE. 
emanations are also accompanied by an ionization of one or 
more of the atmospheric gases, it results that the electrical 
properties of our atmosphere depend in some way upon them. 
In general, therefore, this brilliant chapter in the history of 
research is another illustration of the dependence of meteor- 
ology upon the progress that is being made in every other 
branch of science. So we have now to face a new problem 
in evolution. Laplace taught the evolution of the solar sys- 
tem from a gaseous nebula; Huxley taught the evolution of 
higher forms of life from elementary structures; who will 
now teach us the evolution of the gaseous molecules of the 
atmosphere and the solid elements of the earth, from the 
initial atoms, corpuscles, or electrons? 
MECHANICS OF THE ATMOSPHERE. 
Dynamic meteorology deals essentially with the study of 
the behavior of a true gas, dilatable with heat and compressi- 
ble with pressure, but mixed with small and variable per- 
centages of vapors that condense to liquids or solids at ordi- 
nary low temperatures. The problems of modern meteor- 
ology therefore lie in the field of aerodynamics and thermo- 
dynamics, and can only be solved in proportion as our 
knowledge of experimental physics shall be extended. But 
the proper treatment of these problems also involves the 
application of difficult branches of mathematics and ana- 
lytic mechanics, and these subjects have not yet been devel- 
oped to an extent sufficient to handle any but the simplest of 
the problems of nature. As we read the scientific literature 
of the eighteenth century we find Euler, in his “Mechanics” 
(1736), developing the fundamental formulae for the move- 
ments of dry gases and ideal liquids, after he had proceeded 
as far as he could with the mechanics of rigid bodies. In his 
prize essay of 1746 D’Alembert developed a theory of the 
winds. We pass then to the great French mathematicians, 
Lagrange, Poisson, and Laplace, and the English mathema- 
ticians, Green and Stokes, to all of whom we owe investiga- 
tions of the laws of motions of fluids under two essentially 
tially different conditions, namely, when a velocity potential 
