Show TRAVEL ACCORDING TO MAP airmen on night raids have course thoroughly mapped out before beginning their journey before leava leaving on a long distance night raid that airmen prepare their maps with arfat care marking on oil them the detailed course from the airdrome to their by means 04 oy small balloon whose speed direction and height Is record iii d by an inspru instrument ment on the ground the force and direction of the wind fit at different altitude Is discovered and the compass coura county allowing for inal drift Is marked beside the course ou on the map the compass tom pass course for the return Journ journals 4 ls also marked the speed of the in chine Is calculated nn ant 1 l on the line of ozithe he course a series of points Is mar marked d showing where the tj 1 machine shout be every ten minutes thus enabling uie the airman to check bl hia progress and t inov ills his position if 1 he be bets ets lost lie he watches vatch esho she country below for landmarks up sees by ills his map tatt a L river in a few minutes t ills va shows that lie lias been flying and near the 45 minute marn maroon his map Is a twisted pale blue lne lie ile looks ahead and sees in the moonlight a silver streak and lie he klows he Is making good time when 14 la Is over the river he compares its outline with his mari map and see sees that flint i Is crossing it at the right place sf |