THE NATIONAL GEOGRAPHIC MAGAZINE 



91 



TRUCKING TONS OF TNT AT A U. S. NAVAL BASE IN SCOTLAND 



These black globes of imprisoned death will be attached to their box anchors and then trans- 

 ferred to the mine-laying vessels of the American Navy. 



box-like anchor slowly sinks. Inside the 

 anchor the mooring wire is wound on a 

 reel, which mrwinds as the anchor goes 

 down. This reel is unlatched by the 

 downward pull of a plummet at the end 

 of a cord, which is made the same length 

 that it is desired to have the mine stay 

 below the surface. Thus, if the mine is 

 to be 15 feet beneath the surface, the 

 plummet cord is 15 feet long. 



The plummet, being nearly solid and 

 quite heavy, about 90 pounds, tends to 

 sink faster than the more bulky anchor, 

 thus keeping the cord taut ; but as soon 

 as the plummet strikes bottom, its cord 

 is at once slackened, releasing the latch, 

 locking the reel, and preventing any more 

 mooring wire paying out. The anchor 

 continues to sink, pulling the mine case 

 under water until the anchor strikes 

 bottom. 



The mine case is thus finally moored 

 always at the desired depth beneath the 

 surface, no matter how irregular the 

 ocean bed mav be. The mermaids would 



see our summer's work like a vast field 

 of tulip buds 50 feet or so under water, 

 swaying on their long, slender stems. 



The mine cases are buoyant enough to 

 pull straight up from their anchors ordi- 

 narily, but in a current they are swayed 

 away from the vertical, which drags them 

 down somewhat deeper than intended. 

 For this reason, any locality where the 

 currents are strong is unfavorable for a 

 mine field. This was one of the difficul- 

 ties the British Navy had to contend with 

 in closing the Straits of Dover 



To receive the large amount of mine 

 material and general supplies that soon 

 began to collect, a large steamship pier 

 was taken over at Norfolk, to serve as a 

 storage as well as loading point. 



Near by a plant was constructed for 

 charging the mine spheres with explo- 

 sive — great steam kettles for melting the 

 TNT, which was poured into the spheres. 

 Then these would move along on a con- 

 veyor, slowly, so that by the time the 

 sphere reached the end it was cool enough 



