Something in the tone in which these last words were spoken struck Arnold with a kind of cold chill, and he shivered slightly as he said in answer to Colston-- "I am ready when you are, and no less anxious than you to set eyes on my model. I hope to goodness it is all safe! Do you know, when I am away from it I feel just like a woman away from her first baby." A few minutes later two of the most dangerous enemies of Society alive were walking quietly along the Embankment towards Blackfriars, smoking their cigars and chatting as conventionally as though there were no such things on earth as tyranny and oppression, and their necessarily ever-present enemies conspiracy and brooding revolution. CHAPTER IV. THE HOUSE ON CLAPHAM COMMON. Twenty minutes' walk took Arnold and Colston to the door of the tenement-house in which the former had lived since his fast-dwindling store of money had convinced him of the necessity of bringing his expenses down to the lowest possible limit if he wished to keep up the struggle with fate very much longer. As they mounted the dirty, evil-smelling staircase, Colston said-- "Phew! Verily you are a hero of science if you have brought yourself to live in a hole like this for a couple of years rather than give up your dream, and grow fat on the loaves and fishes of conventionality." "This is a palace compared with some of the rookeries about here," replied Arnold, with a laugh. "The march of progress seems to have left this half of London behind as hopeless. Ten years ago there were a good many thousands of highly respectable mediocrities living on this side of the river, but now I am told that the glory has departed from the very best of its localities, and given them up to various degrees of squalor. Vice, poverty, and misery seem to gravitate naturally southward in London. I don't know why, but they do. Well, here is the door of my humble den." As he spoke he put the key in the lock, and opened the door, bidding his companion enter as he did so. Arnold's anxiety was soon relieved by finding the precious model untouched in its resting-place, and it was at once brought out. Colston was delighted beyond his powers of expression with the marvellous ingenuity with which the miracle of mechanical skill was contrived and put together; and when Arnold, after showing and explaining to him all the various parts of the mechanism and the external structure, at length set the engine working, and the air-ship rose gracefully from the floor and began to sail round the room in the wide circle to which it was confined by its mooring-line, he stared at it for several minutes in wondering silence, following it round and round with his eyes, and then he said in a voice from which he vainly strove to banish the signs of the emotion that possessed him-- "It is the last miracle of science! With a few such ships as that one could conquer the world in a month!"