192 ANNUAL OF SCIENTIFIC DISCOVERY. 



hallooed, it was followed by a distant echo, and even this served as a differ- 

 ential index to height." 



At A. M., on the morning of the 2d, the voyagers arrived at the shore of 

 Lake Erie, a little north of Sandusky. The course was at first held along 

 the southern shore of the lake; but by 10.20 the lake was crossed, and the 

 Canada shore reached. In attempting to make a landing in the vicinity of 

 Rochester, N. Y., the aeronauts encountered a hurricane, and after being 

 blown for a great distance, a part of the time over and near the surface of 

 the lake, they brought up in a forest in the town of Henderson, Jefferson 

 County, X. Y. None of the party were seriously injured, but the balloon 

 was nearly destroyed. The entire distance travelled, from St. Louis to the 

 point of landing, was eleven hundred and fifty miles, which was done in 

 nineteen hours and fifty minutes, being very nearly a mile per minute. The 

 longest journey heretofore made in a balloon was five hundred miles, per- 

 formed many years ago by Mr. Green, the well-known English aeronaut. 



ON THE FORM AND FLIGHT OF PROJECTILES FROM RIFLED CANNON. 



From a recent work on rifled cannon, published in England by Mr. 

 Thomas, we derive the following memoranda relative to the construction of 

 the projectiles to be used in connection with this new ordnance. 



In the practical adaptation of these new engines of war, it must be remem- 

 bered that it is the gun, rather than the shot, which has to be carefully 

 studied; because, for the production of great velocities, heavy charges of 

 powder are required, and these again demand greater thickness and there- 

 fore greater weight to enable the gun to withstand the greatly increased 

 strain upon it. Hence, the object is to obtain such a projectile that it can 

 be thrown from a gun of the same weight as that which throws the round 

 shot, but which shall be, at the same time, a much heavier missile. " Xow 

 this," adds Mr. Thomas, " can be accomplished by the use of elongated shot 

 shot in which, while the weight is the same as that of the 32 Ib. sliot, the 

 diameter is only that of a 9 Ib. shot; and therefore the surface, upon which 

 the resistance of the air acts, will be the same, or nearly the same, for the 

 heavy shot as for the lighter. 



To secure the accurate flight of an elongated missile, it is of paramount 

 necessity to keep its axis coincident with the line of its fl ght; for, if this be 

 not attended to, the resistance of the air becomes greater, and the shot is 

 liable to turn over on its shorter axis. To maintain this coincidence, the 

 projectile mu*t be made to rotate upon its axis; and this rotation can only 

 be obtained by means of the turn or twist it acquires during its constrained 

 passage alonj; the rifled grooves of the gun's barrel. Again, as this rotation 

 varies accordinir to the length of the turn given, it becomes of primary im- 

 portance to determine accurately how much the turn should be, and whether 

 it shoui.l be the same or different, according to the cannon or the projectile 

 require 1. Mr. Thomas, who has paid especial attention to this question, 

 states that the lengths of turn now in use vary between that of the Enn'eld 

 bullet, which has one turn in seventy-eight inches, and those adopted by 

 M ijoi' Jacop and Mr. AVhitworth. which are, respectively, one in twenty-four 

 and one in twenty inch"*, lie point* out that this remarkable disparity 

 arises, in a great measure, from the difference in the shapes of the bullets ; 

 and sums up his whole investigation with two general conclusions fir*t, 

 that the velocity of rotation, or, in other words, the appropriate turn, must 



