above 300 degrees, and 20 lbs. not quite 260 degrees; therefore there would be a full 40 degrees of surplus to ensure the temperature. I have a great tendency to believe in the advantage of further heating even, which might be done by a Perkins’ arrangement of hot water; but possibly the new conditions, as regards oiling, &c., might involve difficulties not desirable to introduce in this case. In the boilers it will also be necessary to adopt every refinement which has been found really to answer, although not always adopted; above all, every means of keeping them clean--scum pans, and Field’s exchanging apparatus. But what would be even more effectual would be some easy means of removing a whole bundle of tubes and replacing them by clean ones; and surely this would not be difficult, the tubes being large and with plenty of space, so that a man could pass his arm between. A rather important addition to boilers would also be a means of blowing off without noise. Several modes would seem to be possible, but whatever plan is adopted, it should be one which is completely self-acting, and perfectly effectual when used suddenly and without any preparation, and at a moment of confusion and alarm. Blowing through a wire gauze pipe would probably be as likely a way as any.[149] The more consideration I give to the subject the more disposed I am to adopt oscillating engines for both screw and paddles. The extreme simplicity and small number of parts, and compactness, and the direct action of every resistance to the force which it is wanted to resist, seem to leave nothing to be desired, and would seem to make it a better and more mechanical arrangement of a cylinder and crank than any other, quite independently of the object for which it was originally designed, which was simply ‘stumpiness.’ _February 21._--The original line (to Calcutta) seems likely, after all, as usual with most original ideas, to be the best; at all events, so good that the vessel must be built to be able to go there. The dimensions best fitted for this would seem to be--length, 700 feet; beam, 85 feet; depth of hold, 58 feet; screw, 24 feet; paddle 60 feet. If arranged for Calcutta, we must arrive there on an even keel, and therefore, to maintain the most equal level for the paddles, they must be kept well forward, and the change principally at the stern. Engines indicated horse-power 8,000; steam at 25 lbs.; auxiliary steam at 60 lbs.