124 
NATURE 
[ApRiL, 4, 1912 
THE INSTITUTION OF 
ARCHITECTS. 
pate annual meeting of the Institution of Naval 
Architects opened on Wednesday, March 27, at 
the Royal Society of Arts, and extended over Thurs- 
day and Friday. The annual gold medal of the 
institution was presented to Prof. E. G. Coker for 
his paper on the determination of stresses by the 
photo-elastic method. Premiums were also awarded 
to Mr. C. E. Inglis and Mr. J. Montgomerie for 
papers read at the last spring meeting. The first 
award of a scholarship of 2001. per annum from the 
1851 Exhibition Commissioners has been made to 
Mr. Arthur Cannon on the recommendation of the 
council of the institution. Mr. Cannon is pursuing 
a course of résearch work at Glasgow University in 
problems connected with the rolling of ships, and 
read a preliminary paper at this meeting on the effect 
of an internal free fluid upon the initial stability. 
The president (the Marquis of Bristol) delivered an 
address in which he directed attention to the record 
in shipbuilding achieved during the past year. Mer- 
chant shipping launched in the United Kingdom 
advanced by 58 per cent., and warships by 71 per 
cent., as compared with the previous year. There is 
no lack of orders at present, but the labour unrest 
threatens to arrest many of the benefits which should 
follow on the recent revival of trade. 
Admiral Sir Reginald Custance, in his paper on 
some military principles which bear on warship 
design, advocated the development of fire effect to 
the fullest extent possible. The decline in the value 
of armour and its possible reduction, coupled with 
the increased range and power of modern guns, are 
the changed conditions which may enable a return 
to be made to this old and well-tried principle. There 
is reason to doubt whether batteries of comparatively 
few large guns form the most effective armament. 
The admiral’s views that armour, speed, and size of 
guns should be sacrificed in order to secure more 
guns were strongly contested by several speakers. 
A paper on the law of comparison for surface 
friction and eddy-making resistances in fluids was 
read by Dr. T. E. Stanton. The prediction of wave- 
making resistance from experiments on models 
according to Froude’s law of comparison is usually 
carefully treated by authorities on naval architecture, 
but there does not appear to be any suggestion of a 
similar treatment of the surface friction and eddy- 
making problem. Prof. Osborne Reynolds showed 
nearly thirty years ago that, in two pipes in which 
the lengths, diameters, and surface irregularities 
were in a given constant ratio to each other, if the 
velocities were made in the inverse of this ratio, the 
total frictional force was the same for each pipe. 
Lord Rayleigh has shown that, in cases where there 
is no resistance due to surface waves and the velocity 
is not high enough to produce cavitation, the resist- 
ance per unit area can be expressed by 
R=}pV°k, 
where k is an expression depending solely on He 
NAVAL 
uw being the coefficient of viscosity of the fluid and 
p its density. This law of comparison applies equally 
well to cases in which the resistance is made up 
partly of surface friction and partly of eddy making. 
Experimental verifications of the truth of this relation 
have been obtained at the National Physical Labora- 
tory in two cases, viz., the determination of the 
frictional resistance of two different fluids (air and 
water) on the same surface, and the total resistance 
in water of models of a dirigible balloon to different 
scales. The latter tests are of particular interest. 
NO. 2214, VOL. 89] 
Two models of the same dirigible to different scales 
were towed in the experimental tank and their resist- 
ances measured. If the law of comparison holds, 
their resistances will be equal for the same value of 
vl, and this was found to be the case very closely. It 
thus becomes possible to estimate the resistance in 
air of a dirigible balloon by experiments in which a 
model is towed under water. Obviously the same 
method is applicable to torpedoes and submarines. 
In the course of the last seven years considerable 
data have been collected regarding the rolling of Irish 
lightships. The results were summarised in a paper 
read by Messrs. George Idle and G. S. Baker. (a) 
The greatest rolling amplitudes are attained by the 
old ships, wooden or composite, having double bilge 
logs. These ships have generally small initial stability 
and a low metacentre, and show that the metacentric 
height does not by itself give any indication of the 
ship’s probable behaviour in a heavy sea. (b) Large 
amplitudes are reached when the sea is breaking or con- 
fused and when the waves are advancing on the bows 
or quarters. Maximum amplitudes have been recorded 
when the ship has been nearly head to the advancing 
wave. The differences in amplitude of “head to” 
and ‘‘beam to’’ positions in heavy swells averaged 
16 to 20 degrees for the single oscillation in favour 
of the latter, suggesting that there are causes pro- 
ductive of heavy rolling other than mere assonance 
between the ship and the wave. (c) The greatest 
angle of heel is always away from the advancing 
wave, no matter what may be the direction and force 
of the wind. (d) When the bilge keels are efficient 
the ship’s normal period of oscillation is increased 
by one up to three seconds, sometimes more. The 
amplitudes of roll are generally moderate in this 
increased period. There is apparently an attempt on 
the part of the wave to bring the ship to its own 
period, and the function of the bilge keel is evident 
in the fact that it prevents assonance between the 
ship and the wave. It may be safely asserted that 
without bilge keels these small vessels could scarcely 
live in the seas to which they are sometimes exposed. 
A valuable series of experiments was undertaken last 
year at the William Froude National Tank on a 
model of an actual ship built for the Commissioners 
of Irish Lights. The experiments have been taken 
beyond the immediate requirements of the commis- 
sioners with the view of testing the ordinary equation 
for the decrement of roll per single swing of the 
ship, viz. : 
—30=a0+ bé?, 
6 being the mean angle of swing port and starboard, 
and a and 6 coefficients which depend, the former 
on wave-making resistance and the latter on friction 
and head resistance. The results show discrepancies, 
and that there should probably be a term in 6° if the 
bilge keel is sufficiently near the water line. 
The propulsion of modern vessels is developing 
along various lines, viz. internal-combustion engines, 
the steam turbine with speed-reduction appliances 
interposed between the turbines and the propeller, 
and in steam generation oil fuel finds many advo- 
cates. Papers on the Diesel-engined sea-going vessel 
Selandia and on gas power for ship propulsion were 
read respectively by Messrs. W. I. Knudson and 
A. C. Holzapfel, and Prof. J. H. Biles read a paper 
on the geared turbine Channel steamers, Normannia 
and Hautonia, in which the relative merits are dis- 
cussed of mechanical gearing, electrical transmission, 
and hydraulic transmission for speed reduction 
between the turbine and the propeller shafts. The 
maximum efficiency of electrical transmission is about 
go per cent.; this method may be useful in cases 
where a great range of speed at high efficiency would 
