Our country and its resources; . ilator whenever the gas con-tracts through a change of tempera-ture or of atmospheric pressure sothat a constancy of displacementmay be realized. The ballonnet com-pensates losses of volume, but notones of lift (air being about four-teen times heavier than hydrogen);a decrease of lift can be made goodonly by jettisoning ballast (sand orwater i. An excess of pressure with-in the hull caused by an expansionof the hydrogen is relieved by auto-malic valves, which are fitted toboth hull and ballonnet; but as theballonnet valves open at a less pres-sure than those of
Our country and its resources; . ilator whenever the gas con-tracts through a change of tempera-ture or of atmospheric pressure sothat a constancy of displacementmay be realized. The ballonnet com-pensates losses of volume, but notones of lift (air being about four-teen times heavier than hydrogen);a decrease of lift can be made goodonly by jettisoning ballast (sand orwater i. An excess of pressure with-in the hull caused by an expansionof the hydrogen is relieved by auto-malic valves, which are fitted toboth hull and ballonnet; but as theballonnet valves open at a less pres-sure than those of the hull an excessof pressure will first be relieved byan expulsion of air from the bal-lonnet. If, therefore, the latter hasa sufficient capacity, no losses of yaswill occur in the process of regulat-ing the vertical equilibrium. On sonic pressure airships twoballonnets are fitted, one fore andone abaft, which can respectively bepumped full of air and thus steerthe vessel up and down by staticmeans; it is more common, however,. AERIAL NAVIGATION CHARTS(as shown on the left) are designed and colored to closely resemble theas seen from above {on the right) rround 370 OUB COl NTKY AND ITS RESOURCES to effect this function dynamically,i. c. by fitting the airships sternwith a horizontal rudder, called ehvator, which acts by the virtue ofthe pressure onrushing air exertsupon an inclined plane. In addition
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1917
