internal gas bags. The Russian engineer Kowanko pointed out that the lack of a ballonet would cause stresses on the skin during ascent and descent. Also, the skin was not airtight, The first airship's specifications were: Power: four cylinder engine weighing producing at 480 rpm Volume: Empty weight: Gross lift: Ballast and fuel: Equipment and three people: Net lift: The circumstances of Schwarz's return are unclear; there were reports of a hasty departure from Russia. Second airship in Berlin In 1894, Carl Berg procured a contract to build an airship for the Royal Prussian government, referring to Schwarz as the originator of the idea. Berg already had experience working with the then novel aluminium, and was to later manufacture components for Zeppelin's first airship. With financial and technical help from Berg and his firm, the airship was designed and built. Construction began in 1895 at the Tempelhof field in Berlin. For a time the Prussian Airship Battalion placed its grounds and personnel at Schwarz's disposal. The components were produced in Carl Berg's Eveking Westphalia factory and, under the direction of Schwarz, assembled in Berlin. A gondola, also of aluminium, was fixed to the framework. Attached to the gondola was a Daimler engine that drove aluminium propellers. One of the propellers was used to steer the craft. In June 1896 Carl Berg sent a card to his stepfather from Moscow apparently indicating that he had searched for information on Schwarz and became cynical of delays and was nearly convinced he had been swindled. Due to delays, the airship was first filled with gas and tested on 9 October 1896, but the results were not satisfactory because the hydrogen delivered by the Vereinigte Chemische Fabriken from Leopoldshall (part of Staßfurt) was not of the required purity and so did not provide enough lift. However, some sources claim that a test was performed on 8 October 1896. It was determined that gas with a density of 1.15 kg per cubic metre was needed. Gas of that quality could not be obtained for some time, and a test flight could not be made until November 1897, roughly ten months after Schwarz's death. Death and maiden flight Schwarz did not live to see his airship fly. Between 1892 and 1896 he traveled frequently, which affected his health. Shortly before his death he received news that his airship was ready to be filled with gas. On