586 



Popular Science Monthhj 



Testing the Lifting Capacity 

 of Balloon Fabric 



THE arcomparning photo- 

 graph gives an accurate 

 idea of the great strength of 

 balloon fabric. Six men are 

 shown in a basket suspended 

 from a balloon patch. In the 

 ordinary balloon there are 

 twenty such patches, which 

 means that the huge gas-bag 

 is strong enough, considering 

 only its fabric, to bear the 

 combined weight of one hun- 

 dred and twenty men. 



The photograph is interest- 

 ing from another angle. It 

 shows how the ropes are 

 attached to the fabric. The 

 ends of the ropes are first 

 separated into four strands 

 which are frayed out and 

 sewed to the fabric after 

 wliich another layer of fabric 

 is cemented over it. The 

 basket is designed to accom- 

 modate two persons, yet the 

 combined balloon patches 

 have a lifting capacity of more 

 than ten tons. 



The Night Eyes of the Coast 

 Artillery 



IN ORDER that the coast 

 of the United States may 

 be guarded by night as 

 well as by day, the officers 

 of the Coast Artillery have 

 dc\cloped a type of search- 

 light larger than any hither- 

 to used in the United 

 States Army. The one 

 illustrated is located at 

 F"ort Terry on Plum Island, 

 where the United States 

 maintained a militan,' camp 

 for Ijoys this summer. 



(juardiiig the entrance of 

 the sound there are fifteen 

 such searchlights. L'nder 

 favorable conditions the 

 beam from one of these 

 giant searchers can 

 "pick up" ships at 

 a range of ten thou- 

 sand yards, or almost 

 six miles. Under 



There are 

 twenty patches 

 in each balloon 



ordinary conditions its range is 

 about seven thousand yards. 

 The light itself consists of the 

 barrel, which is a large 

 horizontal cylinder, in the 

 back of which is a great 

 parabolic mirror which meas- 

 ures sixty inches across. The 

 front of the barrel is closed by 

 plate glass. Between the 

 glass and the mirror an arc 

 plays between two horizontal 

 carbons, capable of develop- 

 ing eighty thousand candle- 

 power. The carbons are fed 

 automatically and last for 

 about five hours when the 

 light is in steady use. 



Each searchlight, a unit in 

 itself, is mounted on a truck, 

 by means of which the light 

 may be moved to various 

 points. A motor operating 

 the moving mechanism of the 

 light is connected electrically 

 with the controller which may 

 be at any distance from the 

 light. 



By means of this arrange- 

 ment an officer in an observa- 

 tion tower may manipulate 

 the light in any direction de- 

 sired by using a series of levers. 



Under Tavorablc conditions 

 searchlight can "pick up" sh 



the beam from this giant 

 ips almost six miles distant 



