4:2 ANNUAL OF SCIENTIFIC DISCOVERY. 



surface resembles an arch, which would best compare with a narrow breast- 

 hook timber of a vessel. They are four feet six inches deep by five feet six 

 inches wide the whole length being fifty-seven feet, with forty-five feet from 

 the span of the arch to the ends, and eighteen feet wide across the crotch. A 

 bulkhead, also water and air-tight, is placed through the crotch, dividing the 

 tank into three separate chambers, with a valve under each to admit and let 

 out the water. The valves are opened simultaneously by a lever attached to 

 them all, and, by letting go the lever, are closed by the pressure of the water. 

 The tanks are to be attached one to the bow and the other to the stern of a 

 sunken vessel, each one receiving so much of the vessel within its arch. A 

 sufficient weight is applied to submerge them when filled with water, and 

 when made fast to a vessel or any sunken body, the water within them is 

 expelled by the force of air on its surface, which is to be applied by means of 

 a pump, and which will then give to the tanks their lifting power. They are 

 constructed in the most substantial manner, having heavy timbers with thick 

 planking inside and out, and fastened with two hundred and one inch bolts, 

 from five to seven feet long, over and down the sides, and four two and a 

 quarter inch bolts, eighteen feet long, athwart the crotch. They are calcu- 

 lated to raise under water a barge or other vessel containing four hundred 

 tons of cargo. 



INCREASING THE SPEED OF STEAM-BOATS. 



At a recent meeting of the Royal Society of Edinburgh, a paper on the 

 above subject was read by Robert Aytoun, of which the following is an 

 abstract : 



Mr. Aytoun stated that the proposition in hydraulics, that the power 

 required to impel a boat increases as the square of the velocity, has exer- 

 cised a pernicious influence over the minds of shipbuilders in making them 

 look upon it as hopeless to attempt any great increase of speed, which was to 

 be attended by such enormous increase of power. This proposition, by show- 

 ing the impossibility of greatly increasing speed with any of the known forms 

 of boats, by giving them increased power, clearly indicated that the path of 

 improvement, if any, must lie in new forms, calculated to take advantage of 

 the new power of the marine steam-engine. It at once occurred to him, 

 that by elongating the bow of the vessel, that water which our present steam- 

 boats dash aside from their path with great force and velocity, and the rapid 

 removal of which absorbs the whole power of the engine, might be laid aside 

 comparatively slowly and gently, like the sod from a plough, however great 

 the speed of the vessel. A diagram was shown, exhibiting three steam- 

 boats, whose midship sections were all equal, but the lengths of whose bows 

 were, respectively, 1, 2, 3. It was pointed out that when No. 2 had twice 

 the speed of No. 1, it dashed aside the water in its path with no greater 

 velocity than did No. 1, and therefore did not require more steam power 

 though proceeding at double speed. That when No. 3 had thrice the speed 

 of No. 1, it dashed aside the water in its path with no greater velocity than 

 No. 1, and therefore did not require more steam-power, though proceeding at 

 three times the speed. It thus appeared that the well known proposition 



