"Now," Ned began, "the door to this car must be kept locked except when the train crew are compelled to come through. We, in turn, must be careful about fire and lights. But, for fear of accident, I have taken some precautions."
Alan and Elmer then saw that the top of the case was fitted with a lid the edges of which were bound with rubber. In the center of the covering was a short spout.
"What's the use of an air and gas proof top with a hole in it?" asked Alan, inspecting it curiously.
"Maybe dat's to let de air in and de lid's to keep de hydrogum from gettin' out," volunteered the colored boy.
Ned was too busy to answer the one or to laugh at the other. He had unlocked the lid and thrown it back. About six inches beneath the top of the case stood eight iron boxes—two rows with four boxes in each. These boxes, six inches square, were each about three feet in height and in each could be seen the neck of a glass vessel. Securely packed in their iron jackets to prevent breaking, stood the glass receptacles, open-mouthed and apparently empty. But down below the shadowed rims were soft clouds of gaseous vapor, beneath which reposed the precious contents that had cost Ned over a thousand dollars—the liquid hydrogen.
On top of the square iron buckets was coiled eight or ten feet of rubber hose. Taking it out Ned closed and locked the lid. He then screwed one end of the hose onto the open spout and, springing to the top of the case, passed the other end out of the open ventilator.
"Now," Ned explained, "we are in less danger. Difficult as it is to condense hydrogen, it is more difficult to keep it in liquid form. It constantly seeks to return to gas. In a closed place it might make trouble."
Elmer had already disappeared, with popping eyes and mumbles of protest. Alan proudly exhibited to his friend the results of his share of the work of preparation. Every crate, box, barrel and package was numbered and labeled and securely fastened in place.
On one side of the car stood five large oak tanks, looking like the famous beer tuns of Germany.
"I can make more hydrogen in those than you've got in your black box," Alan exclaimed jokingly.