744 



Popular Science Monthly 



ground, no matter how obliquely; the tester 

 knows that the eccentricity of the fixture, 

 due to its unbalanced distribution of weight, 

 is greater than that of the shell, due to its 

 uneven distribution of metal about its axis. 

 Should it, however, point upward, the 

 reverse is true. 



The weight and offset of the eccentricity 

 weight are proportioned to agree with the 

 maximum allowable variation from perfect 

 balance of the shell, so that, if the weighted 

 end of the fix- 

 ture points 

 upward the 

 shell fails to 

 pass the test, 

 while if the 

 weighted end 

 points toward 

 the ground on 

 coming to 

 rest, the sjiell 

 passes mus- 

 rer. 



How far off 

 balance may 

 the shell be? 

 Ina 120-milli- 

 meter French 

 shell — a pro- 

 jectile slightly 

 less than 4^ 

 inches in di- 

 ameter and 

 weighing, un- 

 loaded, close to 40 pounds — about the dis- 

 tance between two pin scratches placed as 

 close together as possible without touching. 



The balance of the shell lengthwise is 

 more easily found. All that is necessary is 

 to balance the shell on knife edges, much as 

 one would balance a pencil on one's finger. 

 The point of balance must be at a definite 

 distance from the base of the shell. A 

 variation of more than one per cent, in the 

 length is sufficient to disqualify the shell. 



French Official Photo 



What the French have in store for German airmen — the 

 famous French "75" mounted on a motor-truck chassis 



A French "75" Anti-Airplane Gun with 

 a Camouflage Dressing 



THE French have found still another use 

 for the versatile "75." They have 

 mounted it on a motor-truck chassis, 

 heavily armored, and have sent it close to 

 the front to pepper German airplanes. The 

 accompanying illustration shows the new 

 combination of motor-truck and big gun 

 and the crew of three that operate each 

 unit. The 

 truck is 

 painted and 

 covered with 

 boughs to 

 hide it from 

 the eagle eye 

 of the enemy 

 air scout. 



Look close- 

 ly at the pho- 

 tograph and 

 you will see 

 that the 

 truck is pro- 

 vided with 

 stabilizers in 

 the form of 

 iron legs or 

 ''jacks'' 

 which actual- 

 ly anchor the 

 truck body to 

 the ground. 

 These stabilizers are located one behind 

 each rear wheel, one on each side of the 

 truck in front of the rear wheels, and one 

 behind each front wheel. 



When the truck is moving, the stabilizers 

 are carried in an inoperative position, but 

 as soon as the truck stops and the command 

 to attack an enemy squadron of airplanes 

 is given, the six stabilizers are forced into 

 the ground, giving the big gun a firm 

 foundation to fire from. 



Train Your Skin So That It Will Not 

 Be Sensitive to Cold 



ris pretty generally believed that ex- 

 posure to cold and wet weather will 

 bring on the disorder known as a "cold." 

 But sensitiveness to cold is usually due to 

 the fact that the nerve centers controlling 

 the circulation of blood through the skin are 

 over-delicate, and exhibit a sort of hair- 

 trigger reaction to exposure. By accustom- 

 ing the body gradually to cool and later to 

 cold baths, resistance to cold is set up. 



Sixty Miles an Hour Is the Climbing 

 Speed of Flying-Machines 



A MODERN airplane weighing as 

 much as a small touring car without 

 any passengers can climb at the rate of 

 sixty miles an hour. The aviator would 

 say that his machine's rate of ascension is 

 1,300 feet a minute. Such an airplane 

 would have an engine of a brake horse- 

 power of 180. The airplane climbing at 

 sixty miles an hour ascends a gradient of 1 

 in 2> X A to 1 in 4. 



