AERONAUTIC 'CHARTS. The rapid progress of aeronautics demands the develop ment of a system of signals and charts which will enable pilots to find their way in the air and indicate convenient landings, atmospheric conditions, etc. One proposed method involves the construction of special aeronautical charts; another requires merely the establishment of easily visible signals by which the pilot can find his position on the very accurate ordnance maps which are commonly used as standard maps in France and other European countries. In the French system, the country is divided into 258 districts, each of which extends about 38 miles east and west and 24 miles north and south, and is represented by a numbered sec tion of the map.
According to one proposed system of sig nals, a large rectangle having the proportions of the corresponding map section and in the correct relative position to the points of the compass will be marked out on the roof of a balloon shed or other building, or on the ground. The rectangle is marked with the number of the section, and the exact position of the locality in the section is indicated by a conspicuous mark. For example, the towns of Beauvais, in section 32, and Nantes, in section 117, would be indicated as is shown in the drawing. A glance at any one of these signals near which he passes will show the pilot the exact place on the map so that he need not be long lost or go very far astray if the signals are sufficiently numerous. A predetermined course can be .followed without carrying a set of maps. It is necessary only to draw on a
small card a rough outline of the sections crossed by the course and adjacent thereto to mark each section with its proper to mark the positions of the starting and destina tion points and to connect these by a straight line. A diagram for a flight from Orleans to Mourmelon is shown in the drawing. It will be observed that the straight course crosses the northwestern part of section 81. Hence, if the aviator comes to the signal shown in the lower most portion of the drawing, which indicates a point in the southwestern part of section 81, he knows that he has deviated toward the right hand. The map is required only for the pur pose of selecting a good landing place, if the goal is a large town.
If the signals are composed of white lines on a black ground, or conversely, they need not be very large in order to be visible at a considerable distance. A rectangle 12 feet broad and 20 feet long, with lines 20 inches wide and figures 6 feet in height (in actual use at Mourmelon), is easily seen from a dis tance of one mile and an elevation of 600 feet.
For the guidance of aviators and aeronauts at night a German inventor has devised a trans lucent red balloon about 8 feet in diameter, containing an electric light of 100 candles or more, and moored by means of an electric cable. These balloons are easily distinguished from other lights, and from stars, and can be seen from a great distance.