INTERNATIONAL AIR MAP—LALLEMAND. 801 
area of 111 kilometers, or 67 miles, north and south and from 82 to 68 
kilometers (61 to 41 miles) east and west. 
In this system the distortion, which increases as the square of 
the distance from the central meridian, would be 36 times as small 
in the air map as in the world map, since a sheet of the air map covers 
only 1° of longitude instead of 6°. As, however, the scale of the air 
map is five times as large, the errors from this source are reduced to 
one-seventh of those in the world map. 
In order to facilitate handling, each sheet should be cut in half, 
the cutting lines running east and west, each half measuring some 28 
by 38 centimeters (11 by 15 inches). The two half sheets should be 
pasted on either side of a piece of cardboard, and should have the 
name and number of the sheet shown in a conspicuous manner. 
The Aero Club of France have prepared, this year, three trial 
sheets of this map, covering the area to be used in the next military 
maneuvers, with a view to obtaining the remarks of the aviator 
officers previous to publishing a final edition. 
3. AERONAUTICAL MARKS. 
As has been previously mentioned, each mark shall show the 
approximate longitude and polar distance of the point over which 
the aviator is flymg. The sign adopted by the committee consists 
of half a rectangle (fig. 2) reproducing, on a sufficiently large scale, 
the frame of the half sheet of the air map in which the mark lies. 
The sides of this frame appear as broad lines, except the side where 
the cut is, which is shown by a fine dotted line; thus it is easy to 
distinguish between the upper and lower halves of a sheet. In this 
frame a large black dot will indicate the correct position, on the sheet, 
of the mark of the ground. 
The half rectangle is correctly oriented, the small sides, parallel 
to the meridians, being due north and south. 
Two large figures, reading toward the north, will be marked on 
either side of this rectangle, the left one giving the numter of the 
units of degrees of the polar distance, and the right one the number 
of the units of degrees of the longitude. 
The combination of these two figures, forming a number easy to 
read and remember, will be sufficient to define the number of the 
corresponding sheet of the map, and to give the rough coordinates 
of the mark itself. In every case where confusion might exist, each 
of the figures should be underlined. 
Owing to the absence of the digits showing the hundreds and tens 
of degrees of longitude and polar distance, any two marks which are 
10° or a multiple of 10° apart will have the same number. The 
disadvantage of this would not be of great importance. For an 
airman to confuse two such marks would mean that he would make 
