242 THE NEW WORLD OF SCIENCE 



The success of such manoeuvers depended, perhaps, upon skil- 

 ful goniometry. A few seconds of time meant victory or 

 defeat. 



Improvements in Aerogoniometry, or Direction Finding from 

 Airships. Just as ground goniostations were able, in the 

 manner above outlined, to measure the direction of a distant 

 and invisible airship which was emitting radio signals from its 

 trailing antenna; so conversely, it became, to a certain extent, 

 established practice among the Allied air services, during the 

 war, to find the direction of certain beacon radio stations from 

 on board a flying airship, and so, by cross bearings, locate the 

 observer's position over the land or sea. In particular, there 

 were three widely separated beacon radio stations in Great 

 Britain, which, for two minutes^ just before each hour, suc- 

 cessively emitted signals corresponding to certain distinctive 

 letters of the alphabet, on a definite wave length. A flying 

 observer, in cloudy weather, wishing to locate himself at such 

 times, could find the radio bearing of each of these three beacon 

 stations, and so lay down his position on his map to a certain 

 degree of precision. The radio bearing of a beacon station 

 could be measured on a steady airplane course to about one 

 degree of arc. The precision of the fix obtained from cross 

 bearings would, in each case, depend upon the distance of the 

 flying plane from the beacons; but ordinarily a fix within 10 

 kilometers of the actual position was considered satisfactory. 

 A distance of 10 kilometers would be passed over in about three 

 or four minutes of rapid flight. These gonio bearings were 

 obtained from coils mounted on the airplane, and commonly 

 within the fuselage, so arranged as to be rotatable by the 

 observer from his seat. Large airplanes, of the long-distance 

 bombing type, often carried a navigating officer, who, among 

 his other duties, took gonio measurements during flight, when 

 the darkness or cloudiness prevented him from recognizing 

 his position over the ground. It is clear that this method of 

 determining positions during flight by aerogoniometry, largely 

 developed under the pressure of the world fight, will play a 



