INTERNATIONAL AIR MAP—LALLEMAND. 299 
appreciable advantage. In many countries maps on this scale 
already exist, but having been produced with special objects, either 
economical or strategical, they only imperfectly satisfy the wants 
of airmen. A new special map is therefore necessary. A provisional 
model, submitted by the Aero Club of France, showing specially the 
typical buildings by their profile in black, was adopted by the com- 
mittee. 
At my suggestion it was decided that the new map should be a 
subdivision of the International Map of the World, on a scate of 1 
to 1,000,000,* for the production of which, on the happy initiative 
of England, a common agreement was recently arrived at between 
the principal States of the civilized world. 
The ‘‘world map” would furnish index diagrams for the fitting 
together of the sheets of the ‘air map,’’ It would also be useful 
for drawing up schemes for long journeys, or for measuring the dis- 
tance between two widely separated points and obtaining the orienta- 
tion of the line adjoining them. 
The “‘world map” is to be designed with the meter as unit of 
lengths, and the meridian of Greenwich as origin of the longitudes. 
The sheets are limited by meridians drawn out at successive intervals 
of 6°, extending from Greenwich, and by parallels traced out at suc- 
cessive intervals of 4°, reckoning from the Equator. 
The meridian sectors, from longitude 180° east or west of Greenwich, 
are given numbers from 1 to 60, increasing in an easterly direction. 
The zones, extending from the Equator on each side to 88° latitude, 
are given letters from A to V preceded by the words “north or south.” 
The polar areas are lettered Z. Each sheet shall bear the name of 
the locality or most important geographical feature on the territory 
represented, and in addition the number of the sector and the letter 
of the zone crossing each other on the sheet in question. Forexample, 
the sheet of Paris will be named ‘“‘ North M. 31.” 
For each sheet the corresponding part of the terrestrial ellipsoid 
is represented by a modified polyconic projection constructed on its 
central meridian. The meridians are straight lines and the parallels 
arcs of circles the centers of which lie on the prolongation of the cen- 
tral meridian, so that the radius of each one is equal to the generatrix 
of the cone tangent to the ellipsoid along the corresponding parallel. 
The alterations of angles, distances, and areas are practically small 
enough to be neglected. 
On the other hand, the sheets of the air map will be limited by 
meridians and parallels at successive intervals of 1°, reckoned from 
the same origins as for the world map. Each sheet should cover an 
area of 1° of longitude and 1° of latitude. ‘Twenty-four sheets of this 
map will therefore cover the same area as the corresponding sheet of 
1 That is not to say that the air map will be an exact amplification of the world map, but nearly so. 
