"This is my private entrance," announced Whittinghame, touching an almost invisible projection on the wall and causing a secret panel to open. "At one time it was a boast that an Englishman's house was his castle, but that is no longer true. Since I cannot prevent the minions of the Government from entering my house and taking an immense amount of data for some useless purpose, I must protect my own interests by this means. I discovered the secret panel after the under-ground cellars had been opened up from outside. Evidently it was a 'Priest's hole,' or refuge in troublous times. This is a seventeenth century house built over cellars of a much older date. Mind the steps; they are a lot worn in places."
At the lowermost step Whittinghame stopped and unlocked a baize-covered door. A faint buzz greeted Dacre's ears.
"The doors are almost sound-proof," continued his guide. "Wait while I switch on a light."
The brilliant glow from an electric lamp revealed the fact that they were standing in a long narrow passage, with a door at the far end similar to the one that had just been opened.
"You wonder why I use lamps in a house when there is electric lighting in the cellars?" asked Whittinghame, noting the look of surprise on his companion's face. "It's easy to explain. If I had electric fittings installed in the house they would cause comment. By retaining the old-fashioned system of lighting it helps to keep up the deception that this is a remote country house and the home of a simple country gentleman of limited means. This is the retort room," he added, opening the second sound-proof door.
The place reeked of gas. Dacres felt somewhat apprehensive, for there were no visible means of ventilation.
"Quite harmless," said Whittinghame reassuringly. "We use electricity for producing the gas ultra-hydrogen we term it. I had the secret from a German scientist who was unable to sell his priceless formula in his own country. He was regarded as a lunatic, poor fellow. This ultra-hydrogen has, under equal conditions of density and capacity, three times the lifting-power of ordinary hydrogen. Nor is that all: it is absolutely non-inflammable."
"By Jove!" ejaculated Dacres, too surprised to say anything else.
"Yes," continued his companion. "You may well express astonishment. Just think: nine-tenths of the dangers to which an airship is exposed are by this stupendous discovery. Thanks to the practical non-porosity of the ballonettes of the 'Meteor' we have not yet found it necessary to recharge them. We are, however, laying in a reserve supply of ultra-hydrogen and storing it under pressure in cast-steel cylinders."
"Then, what happens when you want to descend?" asked Dacres. "Has not the gas to be released?"