16 SECTIONAL ADDRESSES. 
mechanism of the atmosphere ; a knowledge of the structure of the atom 
has not helped us to understand the physics of the air as we deal with it 
in meteorology; the relationship between mass and charge, the in- 
variability of the velocity of light, four-dimensional space and all the 
other new conceptions which have been responsible for the advance of 
physics, have been of no help to meteorologists in their especial branch of 
science. 
The whole attention of physicists has been so dominated by these new 
ideas, and the vistas of unexplored country which they have opened out 
are so vast, that it is no wonder that physicists have had no interest in 
a domain in which their new tools could not be employed. The conse- 
quence has been that meteorclogy has had little help from physicists and 
mathematicians as such, and has had to depend, in this country at least, 
on the relatively small band of meteorologists in Government employ. 
Let me say, however, that we are grateful for the help which we have 
received from physicists, especially from those who were brought into 
contact with meteorology during the war. In spite of the fact that 
meteorology has not been able to make use of the recent discoveries in 
pure physics, there has been in the last twenty-five years as fundamental 
a revolution in our ideas of the atmosphere as has taken place in our 
ideas of electricity and matter. Unless I am very much mistaken, these 
fundamental changes in our conception of the atmosphere, both as a 
whole and in its parts, are little known outside the small band of pro- 
fessional meteorologists. I therefore welcome this opportunity of bringing 
them before the members of Section A. 
I have chosen as the title of this address ‘ The New Ideas in Meteor- 
ology.’ It is questionable, however, whether the word ‘new’ is a suitable 
adjective to use, for the ideas which I am about to describe deal with 
principles and processes which are by no means new, and the ideas them- 
selves can be traced back to the last century. Nevertheless it is only in 
the last few years, in some cases only since the war, that their significance 
has been realised even by meteorologists. 
I shall divide my address into four parts, each dealing with one of the 
new ideas, namely : 
(1) The thermal stratification of the atmosphere ; 
(2) The mechanism of the atmospheric heat engine ; 
(3) The significance of surfaces of discontinuity in the atmosphere ; 
(4) The origin and structure of cyclones. 
The Thermal Stratification of the Atmosphere. 
The fact that the temperature of the air decreases as we ascend in the 
atmosphere has been known from time immemorial, but our real knowledge 
of the temperature of the free air dates only from 1898, when Teisserenc 
de Bort introduced his ballons-sondes, which carried self-recording instru- 
ments to heights in the atmosphere up to that time never attained and 
from which no information was then available. , 
The initial success of Teisserenc de Bort in his epoch-making discovery 
of the stratosphere attracted great attention to his investigations. His 
methods were introduced into other countries and an intense investigation 
of the upper atmosphere, with an International Commission to guide and _ 
