1913-14.] 
Principia Atmospherica. 
77 
IX.— Principia Atmospherica: a Study of the Circulation of the 
Atmosphere. An Address delivered at the request of the Council 
before the Royal Society of Edinburgh, on 1st December 1913. By 
W. N. Shaw, LL.D., Sc.D. , F.R.S., Director of the Meteorological 
Office, Reader in Meteorology in the University of London. 
(Read December 1, 1913. MS. received December 12, 1913.) 
Introduction. 
Every science has two aspects or two stages in its development. In the 
first, the inductive stage, observations are made and compiled, and axioms or 
laws are laid down. In the second or deductive stage the laws are applied 
by syllogistic reasoning, mathematical or otherwise, to elicit conclusions 
which either disclose new facts or show the inevitable connection between 
facts already known, and, in either case, complete the claim of the study to 
the rank of a science. 
The different sciences vary greatly in the stage of development which 
they present. The science of geometry has almost forgotten the origin of 
its own laws and axioms, and occupies itself with the most complicated 
deductive propositions, the forms of which are used to guide the deductions 
of other sciences. Biology is still in the inductive stage: no one ventures 
yet to predict in what form the horse will be found a million or even a 
thousand years hence. 
These different aspects of science appeal with different force to different 
types of human mind. Observers are comparatively rare ; true inducers, 
those who have the patience and the insight to arrange the facts and 
formulate the underlying laws, are extremely rare; deducers, those who 
draw conclusions, not always mathematical or strictly logical, make up the 
balance of the human race. 
Many years ago, in 1862, Dr Alexander Buchan, in a contribution to this 
Society which was subsequently elaborated in a volume of the results of 
the Challenger Expedition, laid the foundations of our inductive know- 
ledge of the atmospheric circulation by a series of maps of the distribution 
of pressure over the surface of the globe. With great pleasure I take the 
opportunity afforded to me by your invitation to address you on recent 
developments of the science of meteorology, particularly in the investigation 
of the upper air, to put before you a representation of the knowledge of 
