The tank-room of the rocket-ship Berenice , where the big tanks of water-weed were kept, was so spick and span that a man needed little psychology to realize that its manager was a dapper, finicky, careful little man. The room's lights were bright and efficient, the water in the tanks fresh and clean, and there were no decaying fronds of vegetation among the thousands of stems of water-weed which, floating about in the tank, absorbed the carbon dioxide which was pumped through the water, and gav