TRANSACTIONS OF THE SECTIONS. 187 
peinied out by a diagram that, in his opinion, the mode of preventing such an acci- 
ent in future was the employment of double sluices, one behind the other, the 
water between the two being always kept locked in, at a mean height between the 
water in the drain and that on the sea-side, during the time the sea doors are closed 
by the tide; by this mode, the pressure of the highest tide, on each set of doors, 
will be only one-fourth of that on the single set of doors, on the fallen sluice, at the 
time of the disaster. Hence its undoubted safety. 
On the Merits of Wooden and Iron Ships, with regard to cost of repairs and 
ee security for life. By L, WILLrIAMson. 
The author called attention, in particular, to an iron ship, the ‘Santiago,’ which 
met with a collision, the consequences of which would have been absolute destruc- 
tion of the vessel had she been of wood; whereas, being of iron and haying water- 
tight mente, the vessel was able to pursue her voyage, and was repaired at 
the cost of a few hundred pounds, instead of several thousands which would have 
been necessary had she been made of wood and could have been preserved from 
foundering. 
Oblate Projectiles with Cycloidal Rotation, contrasted with Cylindro-ogival 
Projectiles having Helical or Rifle Rotation. By R. W. Woortcomse. 
The object of this paper was further to discuss the views of the author given in 
a paper read before the Royal Society in March last (1862), entitled, “ An Account 
of some Experiments with Excentric Oblate Bodies and Discs as Projectiles,” and 
to show the result of further experiments. Rifled cannon, it appears, cannot project 
heavy elongated shot with high initial velocity; and, except with the Whitworth 
flat-headed shot, the penetration of iron plates can only be effected by means of a 
high velocity. The author considers that however well the helical or rifle method 
with cylindrical elongated shot may answer for small arms, yet that, when we wish 
to project great weights with great and sustained velocities, we shall succeed better 
if our mechanical arrangements are less antagonistic than the rifle principle to the 
great laws of nature, as exhibited in the form, method of rotation, and translation 
of the great natural projectiles, the planets. None of these are prolate bodies pro- 
jected with helical rotation about their longest diameters and in the direction of 
such axis. The author states that he has found it practicable to project a body 
that, instead of being prolate, is more or less oblate,—that, instead of having helical 
rotation at the expense of translation, has cycloidal rotation in ad of translation. 
A projectile, having a circular periphery in the line of motion in the gun, leaves the 
bore as a common round shot, and has the additional security for high initial 
yelocity of windage less than for round shot of similar weight. The terminal 
velocity is also provided for by the oblateness, and by the axis of rotation being 
always transverse to, and not in the plane of, the trajectory. The gun has asimilar 
transverse section to that of the projectile, the bore being straight and smooth. 
The projectile is a disk, and it should be slightly excentric to make it rotate—so 
slight as to be /ittle more than the inevitable excentricity of every spherical projec- 
tile. The author then gave the results of some actual experiments with a gun 
and projectiles made on this principle. The gun was 20} inches long ; the calibre, 
long diameter 12 inch, and short diameter 3 inch. The shot polghad nearly 8 ounces, 
with a charge of 2} ounces, or three-fifths the weight of the shot; the penetration 
at 25 yards from an oak target was a mean of 11 inches, reckoning to the near side 
of the disk, and to the far side nearly 18 inches. 
The initial velocity, measured by Havez’s electro-ballistic apparatus, was 1487 feet 
per second. A comparison was made with a small brass gun, length of bore 
34625 inches, or nearly double the length of the author’s gun in calibres, The 
mean calibre of the brass gun was 1°6 inch, the mean diameter of the round shot 
was 1:43 inch; and this gun, fired with a proportionate charge of powder, showed 
that the disk gun gave more than double the penetration of the brass gun, and an 
initial velocity of 1487 to 1091 of the latter. He thought that these remarkable 
experiments showed that the subject was worthy of further consideration, 
