484 



into a great mesh of basket-work. Six- 

 teen slender members form the longi- 

 tudinals, running from bow to stern, and 

 intersecting the spirals of wooden rope 

 where they cross each other. The func- 

 tion of the spirals and longitudinals 

 acting together is to distribute the gas 

 lift and strains evenly to all points of the 

 hull. 



There are, in reality, two hulls, the 

 inner enclosing thirteen balloonets or 

 gas bags and the outer supporting a 

 waterproof and airtight envelope or 

 skin. Twenty-nine ribs, or transverse 

 girders, encircle the inner hull, and a 

 spider web of wire cables stiffens the 

 alternate ribs and forms the bulkheads 

 between the balloonets. 



Two eight-cylinder, sixty-horsepower 

 motors have been installed, and by 

 means of cable drives transmit the power 

 to four propellers mounted high above 

 the car, two being placed on each side of 

 the slender torpedo-like hull. 



In hot weather, or when the airship 

 passes through a heated stratum of air, 

 the gas expands, exerting more lifting 

 power, and causing the airship to rise. 

 To control this tendency, the gas has to 

 be artificially cooled, or it will be neces- 

 sary to release som.e of the valuable 

 hydrogen to allow the ship to retake its 

 proper altitude. On the contrary, if a 

 sudden wave of cold air strikes the gas 

 bag, the gas immediately contracts, and 

 part of its lifting power is lost. If there 

 is no means for heating the gas and ex- 

 panding it, ballast will have to be 

 dropped from the car, thus compensating 

 the decreased lifting power of the gas 

 by a lighter weight which it has to 

 carry. 



The control of the lifting power of the 

 gas in the MacMechen dirigible is in 

 the heating and cooling process. To 

 keep the h>'drogen from cooling and 

 losing its lifting power, hot vapor from 

 the engine is blown into the foot-wide 

 space between the balloonets and the 

 outer skin of airtight cloth. To cool and 

 condense the gas for descent, or to pre- 

 vent its expansion to an extent that 

 causes an undue inHation of the gas bags, 

 cold air is introduced into the same space 

 by means of a luminum disks with re- 

 volving shutters at the bow and stern. 



It is claimed that by this method of 



Popular Science Monthly 



construction a rigid airship has been 

 built which is one-third lighter than it is 

 possible to build a Zeppelin of the same 

 relative size. The hull and car weigh 

 2,190 pounds, and the gas capacity is 

 108,000 cubic feet, or about one-tenth 

 that of the latest Zeppelin monster. As 

 hydrogen is usually rated by aeronauts, 

 this quantity will lift about three and 

 one-half tons, or seven thousand pounds. 

 With engine equipment and crew, the 

 airship weighs about 5,300 pounds, leav- 

 ing a margin of 1,800 pounds for ballast, 

 explosives and additional fuel. The 

 length of the hull is 236 feet over all. 

 The designers claim that their airship 



SPIDER WEBBING 

 AT BULKHEADS 



will make about seventy miles an hour, 

 or about ten miles an hour faster than 

 the speed of a Zeppelin. 



The Popular Science Monthly be- 

 lieves that this airship will prove disap- 

 pointing to its builders and to the 

 British Government. Previous experi- 

 ments with wooden frames in dirigibles 

 ha\'e proved costly failures. The Zep- 

 pelin's first rival, the Schiitte-Lanz 

 dirigible, was built with wooden frame- 

 work, and proved much heavier than a 

 Zeppelin of the same dimensions. Lami- 

 nated wood was used in the experiment 

 and this was found faulty and discarded. 

 The Zeppelin of to-day is the product of 

 practical experience, as is the second, 

 and successful, Schiitte-Lanz, which 

 discarded the weblike wooden frame for 

 the lighter metal ribs and strakes of the 

 Zeppelin. Such a solid frame as that of 

 the pigmy airship would not do for a 



