One ingenious scheme that was tried was to suspend an observation car under the Zeppelin. The car was about fourteen feet long and five feet in diameter, fitted with a tail to keep it headed in the direction it was towed. It had glass windows forward and there was plenty of room in it for a man to lie at full length and make observations of things below. The car with its observer could be lowered a few thousand feet below the Zeppelin, so that the observer could watch proceedings below, while the airship remained hidden among the clouds. The observer was connected by telephone with the chart-room of the Zeppelin and could report his discoveries or even act as a pilot to direct the course of the ship. But despite everything that could be done, the Zeppelin eventually proved a failure as a war-vessel because it was so very costly to construct and operate and could so easily be destroyed, and the Germans began to build huge airplanes with which bombing-raids could be continued. Strange to say, however, although the Germans were ready to admit the failure of their big airship, when the war stopped the Allies were actually building machines patterned after the Zeppelin, but even larger, and expected to use them for bombing-excursions over Germany. This astonishing turn of the tables was due to the fact that America had made a contribution to aëronautics that solved the one chief drawback of the Zeppelin. A BALLOON GAS THAT WILL NOT BURN When we entered the war against Germany, our allies placed before us all their problems and among them was this one of the highly inflammable airship. Could we not furnish a substitute for hydrogen that would not burn? It was suggested to us that helium would do if we could produce that gas cheaply and in sufficient quantity. Now, helium has a history of its own that is exceedingly interesting. Every now and then the moon bobs its head into our light and we have a solar eclipse. But our satellite is not big enough to cut off all the light of the big luminary and the fiery atmosphere of the sun shows us a brilliant halo all around the black disk of the moon. Long ago, astronomers analyzed this flaming atmosphere with the spectroscope, and by the different bands of light that appeared they were able to determine what gases were present in the sun's atmosphere. But there was one band of bright yellow which they could not identify. Evidently this was produced by a gas unknown on earth, and they called it "helium" or "sun" gas.