474 = Miscellaneous Intelligence. 
yielded passively to that tendency, like a broad and shallow raft, 
ship has, like a pendulum, a natural period of none depen 
on her stiffness, or tendency to right herself, an ment of 
inertia, nsese: a quantity depending on the distribution of re mass. 
Stiffness tends to shorten, and inertia to lengthen, the period. It 
was asaiee? in 1862, by Mr. F roude, that the greatest unsteadiness 
and the greatest danger of being overturned takes place when the 
periodic times of rolling of the ship and of the waves are equal; 
for then each successive wave adds to the extent of roll; and if 
the co-graaaatly of the periods were exact, the ship would inevitably 
be o rturned in the end. 
her natural Tolling ; ; but great angles of roll occupy longer pores 
than small.* Hence, supposing a ship to encounter waves of @ 
at pe 
creased, un 
time of the waves ; and thus she in a manner eludes the danger 
arising from coincidence of riods. In order, however, that this 
safeguard may act efficiently, it is essential that the natural Lapa 
of the ship for the smallest angles of roll should not be less 
the period of the waves; otherwise the first effect of the progressive 
ase of angle will be, not to destroy, but to produce pain 
cae of period; and the result will be great unsteadiness of m 
tion, and possibl at danger. 
The speaker described the above principles as being the latest 
nangeda to our knowledge of the theory of the relations between 
sea-waves; and he illustrated them by means of expert: 
ments on a machine so constructed as to imitate the dynamical 
es. 
- On a Meteor seen at peg ake Fegupt s by Beverty KEN- 
From 3 pct 
_ * An exception to this rule exists in the case of that form of ship known a8 me 
« Symondite,” i in Which the sides flare out at and near the water-line, so as to mare 
the stiffness ss increase faster than the angle of heel. In such ships the i 
e angle increases; aud 1-1 gues 
Siiias Gadetis of that andal la caeceee for nas Ww . - 
_ periodic time for the smallest of roll is — than that of any of the bei 
which she encounters, the Symons. model does not promote unsteadiness; 
ate he pore ot pec 2 ean ormistwoadiny! ports from coincidence 
