Geography of the Air. 51 
Tiesserene de Bort has continued his work, of improving 
weather forecasts for France, by studying the distribution of the 
great and important centres of high pressures, which prevail gen- 
erally over the middle Atlantic ocean, and, at certain periods of 
the year, over Asia, Europe, and North America. His studies 
have proceeded on the theory that the displacements of centres 
of high pressure, whether in Asia, over the Azores, near Ber- 
muda, in North America, or in the Polar regions, set up a series 
of secondary displacements, which necessarily cause storm cen- 
tres to follow certain routes. M. de Bort concludes that a daily 
knowledge of the relation of these centres and their areas of dis- 
placement will eventually enable skilled meteorologists to deduce 
the position of unknown and secondary centres. He has endeavy- 
ored to reduce these various displacements to a series of types 
and has made very considerable progress in this classification. 
Daily charts covering many years of observations have been pre- 
pared, and these separated, whenever the characteristics are 
sufficiently pronounced, into corresponding types. This plan of 
forecasting necessitates extended meteorological information 
daily, which France obtains not only from Russia, Algeria, Italy 
and Great Britain, but, through the codperation of United 
States, from North America. The daily information sent by the 
Signal Office shows, in addition to the general weather over the 
United States and Canada, the conditions on the western half of 
the North Atlantic ocean, as determined by observations made 
on the great steamships, and furnished voluntarily by their 
officers to the Signal Office through the Hydrographic Office and 
the New York Herald weather bureau. 
The study of thunder storms has received very elaborate and 
extensive consideration. M. Ciro Ferari in Italy finds that 
almost invariably the storms come from directions between north 
and northwest, the tendency in northern Italy being directly 
from the west, and in the more southern sections from the north- 
west. The velocities of storm movements are much greater 
from the west than from the east, considerably more so in the 
centre and south of Italy than in the north; and in the months, 
largest in July. 
The velocity of propagation increases with greater velocities 
of the winds accompanying the storms, with also greater attend- 
ant electrical intensity. The front line of propagation while 
more often curved, is sometimes straight and sometimes zigzag, 
