562 NAROTRE [APRIL II, 1907 
about the axis. The amplitude of oscillation of BRITISH NESTS AND EGGS.’ 
the gyroscope, as Sir William W hite proceeded to HIS handsome and exquisitely illustrated volume 
point out, depends upon many conditions, among (which is practically a new work, so greatly 
which the period of oscillation and its ratio | does it exceed its predecessor in bulk and in wealth 
to the period of rolling of the vessel are | of jflustration) makes its appearance, no doubt pur- 
important. posely, at an opportune time, and if it induces but 
In order to utilise the gyroscopic effect in checking 
rolling it is necessary to have a means of braking the 
apparatus so as to check movement on its trunnions 
and the rotary motion of the fly-wheel. To control 
the swinging motion a simple band-brake was fitted, 
the drum for which is shown on the left of Fig. 1. 
In addition to this a socket was fitted on each side 
of the gyroscope casing below the fly-wheel, the 
braking effect being supplied by hydraulic power and 
regulated by a valve. With the casing held by the 
brake the gyroscope would have no “effect on the 
rolling motion, but on the friction band being 
loosened the casing would oscillate on its athwart- 
ship trunnions, and the gyroscopic action would come 
into play. Sir William White says that, when stand- 
ing upon the deck, which maintained a practically 
horizontal position, the vessel heaving vertically, 
it was curious to notice that though the gyro- 
scope might be oscillating longitudinally the im- 
pression was conveyed that the vessel herself was 
pitching. 
Stilil-water rolling experiments were made with the | 
Seebar, rolling being set up by the crew running 
from side to side. With the gyroscope fixed, the 
period of a complete double roll was found to be 
4-136 seconds. When the fly-wheel was running 
1600 revolutions per minute, the period was six 
seconds. The boat was next hove down by a crane 
to an inclination of 10° to 15° from the vertical, and 
when let go the successive Beanie inclinations were 
noted until they fell to about 3°. 
The still-water rolling experiments strikingly illus- 
trated the enormous extinctive effect of the gyroscope, 
as shown by a diagram given by the author of the 
paper. Selecting two experiments for illustration, it 
was found that with “ 
of 10° with the gyroscope at rest 20 single oscilla- 
tions took place before the extreme inclination to 
the vertical was reduced to half a degree; whereas 
the same amount of extinction was obtained with 
little more than two single oscillations when the 
gyroscope was free to oscillate and the fly-wheel was 
rotating at 1600 revolutions per minute.”’ 
In Fig. 2 we reproduce from Sir William White’s 
paper a graphic record of rolling experiments made 
with the Seebar off Cuxhaven. The point marked 
.B denotes the time when the brake band was re- 
leased, the gyroscopic wheel becoming free to swing 
on its trunnions, and the extinctive forces coming 
into action. The revolutions were 1600 per minute, 
and, as will be gathered, the practical result was to 
extinguish the rolling motion almost immediately, 
although the vessel was naturally still subject to 
heaving motion. The inclinations were insignificant, 
varying from about 3° to 1°. 
Sir William White in his paper discussed the 
further application of the apparatus to war vessels, 
and though he did not commit himself to any definite 
opinion, it may be said that the impression given 
was decidedly of a hopeful nature. In connection 
with this subject the experiments of Sir John Thorny- 
croft with his steam yacht, the Cecile, and those of 
the late Mr. Beauchamp Tower with his hydraulic 
steady gun platform. controlled gyroscopically, will 
doubtless be remembered. Particulars of both series 
of investigations are to be found in the Transactions 
of the Institution of Naval Architects. 
G. 
55 
R. DUNELL. 
NO. 1954, VOL. 
at | 
an initial angle of inclination | 
half-a-dozen collectors in the coming season to devote 
their attention to photographing the nests of our 
native birds in place of robbing their eggs, it will 
have done a great service to British ornithology. 
According to the letter of an admirer quoted in the 
preface, such a conversion has already taken place 
in several instances as the result of the Messrs. 
Kearton’s previous works, and an extension of the 
new practice may therefore be confidently awaited. 
Mr. Kearton observes that ‘“‘it is a curious kind of 
morality that will scorn to steal from the individual 
From ‘‘ British Birds’ Nests.” 
Ptarmigan on Nest. 
and yet rob the community without compunction. 
Wild birds are national property, and no individual 
has a right to harm one of them without the sanction 
of the law to do so.’’ Although this is, no doubt, to 
a great extent true, it must be remembered that by 
nature we are all essentially hunters and _ spoilers, 
and as many of us, at any rate, have not yet fully 
imbibed the socialistic spirit, it would not do for the 
present to be too hard on the egg-collector if he con- 
ducts his operations with moderation. Festina lente 
is an admirable motto in this and many other matters. 
As regards the book itself, a critic is frequently 
embarrassed as to what he should write from the 
intrinsic badness of the work set before him; in the 
present instance the reverse of this is the case, and 
1 “British Birds’ Nests, How, Where and When to Find and Identify 
Them.” By R. Kearton. New edition, revised and enlarged. Pp. xii- 
520; illustrated. (London: Cassell and Co., Ltd., 1907.) Price 21s. net 
