Presently a dust-begrimed collier shook herself free from the moorings which held her to one of the battleships, and, floundering nervously as though anxious to get out of the way as quickly as possible, nosed off into the sooty wakes of three of her untidy sisters who had been coaling the other ships of the division. Shortly the Engineer-Commander, his immediate duties at an end for the moment, came up for a breath of fresh air, and fell into step with me on the quarter-deck. "There you have (so far as the Navy is concerned) the Alpha and the Omega of the coal," he said, motioning with his mittened hand, first toward the retiring colliers, and then, with a sweeping gesture, to where the thickening smoke-columns were beginning to blend in a murky stratum of streaky black above the even lines of the anchored ships. "All the energy (save only human force, and that stored in food and explosives) of the Fleet comes aboard from its colliers or oilers," he continued; "all that is left of it--after making steam to run the turbines and dynamos, and for working the condensers, cooking, and heating--goes up through the funnels or down through the clinker hoppers." Then he told me of an incident which had occurred a day or two previously. "Some one came into the wardroom," he said, "and remarked casually that the wireless had just picked up a signal from a ship about to go ashore in the heavy storm then driving outside. 'What is she?' several officers asked with quick concern. 'Only a collier,' was the reply, and everybody, reassured, resumed the reading of their newly arrived papers. 'I was afraid it was a destroyer,' was the only comment any one made. "That is just to show," said the Engineer-Commander, "how few in a warship (save those of us whose work is the conversion of it into energy) stop to think how vitally important coal really is to us. As a matter of fact, one can easily imagine circumstances in which the loss of a collier would be far more serious than that of a destroyer, cruiser, or even of a battleship." It will doubtless surprise one not already informed in the matter to know that the average modern battleship lying at anchor and waiting to be ordered to sea may easily consume twenty-five tons of coal a day, which figure will be raised from 50 to 100 per cent. by one or two harbour spins at half or quarter-speed for target practice. The condensers make the greatest demand for coal in a battleship not under steam, with the running of dynamos for the numerous and constantly increasing electrical devices next in order. The galleys where the cooking and baking is done, are third on the list of consumers, with the cheery open grates--which are installed wherever practicable--accounting for the remainder.