The Endymion is 360 ft. by 60 ft., with coal capacity for 2,800 miles at 18 knot speed, or for about 144 hours or six days. The enlarged Endymion for the same voyage of 2,800 miles in five days, or at 211/2 knot speed, would be 44 per cent larger and broader, that is 520 ft. by 86 ft., and of threefold tonnage, and three and a half times, or about 30,000 horse power--about the dimensions of the Furst Bismarck, but much more powerfully engined. This agrees fairly with the estimate in the SCIENTIFIC AMERICAN of 19th Sept, 1891., where it is stated that twenty-two boilers, at a working pressure of 180 lb. on the square inch, would be required, allowing 11/2 lb. of coal per horse power hour. The Intrepid, enlarged to a 24 knot boat, for the same length of voyage of 3,000 miles, would be 650 ft. by 100 ft., 40,000 tons, and about 45,000 horse power. So now we are nearing the Messrs. Thomson design in the Naval Exhibition of the five-day steamer, 231/2 knot speed, 630 ft. by 73 ft., and 30,000 to 40,000 horse power. No one doubts the ability of our shipbuilding yards to turn out these monsters; and on the measured mile, and for a good long distance, we shall certainly see the contract speeds attained and some excelled. But the whole difficulty turns on the question of the coal capacity, and whether it is sufficient to last for even five days or for 3,000 miles. Every effort then must be made to shorten the length of the voyage from port to port; and we may yet see Galway and Halifax, only 2,200 miles apart, once more mentioned as the starting points of the voyage as of old, in the earliest days of steam navigation. In those days the question of fuel supply was a difficulty, even at the then slow speeds, in consequence of the wasteful character of the engines, burning from 7 lb. of coal and upward per horse power hour. Dr. Lardner's calculations, based upon the average performance of those days, justified him in saying that steam navigation could not pay--as was really the case until the introduction of the compound engine.