528 
NATURE 
[SEPTEMBER 28, 1899 
can’ be successfully employed ; and to indicate how the experience 
and-achievement of the last sixty years bear upon the prospects 
of further advance. 
There is reason to hope that this choice of subject is not 
inappropriate. From the beginning of steam navigation the 
British Association in its corporate capacity, by the appointment 
of special committees, and by the action of individual members; 
has greatly assisted the scientific treatment of steamship design. 
Valuable contributions bearing on the resistance offered by water 
to the motion of ships, the conduct and analysis of the results of 
steamship trials, the efficiency of propellers and cognate subjects 
have been published in the Reports of the Association. Many 
of these have largely influenced practice, and most of them may 
be claimed as the work of this Section. 
On this occasion no attempt will be made either to summarise 
or appraise the work that has been done. It must suffice to 
mention the names of three men to whom naval architects are 
deeply indebted, and whose labours are ended—Scott Russell, 
Rankine, and William Froude. Each of them did good work, 
but to Froude we owe the device and application of the method 
of model experiment with ships and propellers, by means of 
which the design of vessels of novel types and unprecedented 
speeds can now be undertaken with greater confidence than 
heretofore. 
As speeds increase, each succeeding step in the ascending 
scale becomes more difficult, and the rate of increase in the 
power to be developed rapidly augments. Looking back on 
what has been achieved, it is impossible to overrate the courage 
and skill displayed by the pioneers of steam navigation, who had 
at first to face the unknown, and always to depend almost entirely 
on experience gained with actual ships, when they undertook 
the production of swifter vessels. Their successors of the 
present day have equal need to make a thorough study of the 
performances of steamships both in smooth water and at sea. 
In many ways they have to face greater difficulties than their 
predecessors, as ships increase in size and speed. On the other 
hand, they have the accumulated experience of sixty years to 
draw upon, the benefit of improved methods of trials of. steam- 
ships, the advantage of scientific procedure in the record and 
analysis of such trials and the assistance of model experiments. 
Steamship design to be successful must always be based on 
experiment and experience as well as on scientific principles and 
processes. It involves problems of endless variety and great 
complexity. The services to be performed by steamships differ 
in character, and demand the production of many distinct types 
of ships and propelling apparatus. In all these types, however, 
there is one common requirement—the attainment of a specified 
speed. And in all types there has been a continuous demand 
for higher speed. 
Stated broadly, the task set before the naval architect in the 
design of any steamship is to fulfil certain conditions of speed in 
a ship which shall not merely carry fuel sufficient to traverse a 
specified distance at that speed, but which shall carry a specified 
load on a limited draught of water. Speed, load, power and 
fuel supply are all related ; the two last have to be determined 
in each case. In some instances other limiting conditions are 
imposed affecting length, breadth or depth. In all cases there 
are three separate efficiencies to be considered: those of the 
ship as influenced by her form; of the propelling apparatus, 
including the generation of. steam in the boilers and its utilisa- 
tion in the engines ; and of the propellers. Besides these con- 
siderations, the designer has to take account of the materials and 
structural arrangements which will best secure the association of 
lightness with strength in the hull of the vessel. He must select 
«hose types of engines and boilers best adapted for the service 
proposed. Here the choice must be influenced by the length of 
the voyage, as well as the exposure it may involve to storm and 
stress. Obviously the conditions to be fulfilled in an ocean- 
going passenger steamer of the highest speed, and in a cross- 
Channel steamer designed to make short runs at high speed in 
comparatively sheltered waters, must be radically different. And 
so must be the conditions ina swilt sea-going cruiser of large size 
and great coal endurance, from those best adapted for a torpedo 
boat or destroyer. There is, in fact, no general rule applicable 
to all classes of steamships : each must be considered and dealt 
with independently, in the light of the latest experience and 
improvements. For merchant ships there is always the com- 
mercial consideration—Will it pay ? For warships there is the 
corresponding inquiry—Will the cost be justified by the fighting 
power and efficiency ? 
NO. 1561, VOL. 60] 
Charactiristics of Progress in Steam Navigation. 
Looking at the results so far attained, it may be said that 
progress in steam navigation has been marked by the following 
characteristics :— 
(1) Growth in dimensions and weights of ships, and large 
increase in engine-power, as speeds have been raised. 
(2) Improvements in marine engineering accompanying 
increase of steam pressure, Economy of fuel and reduction in 
the weight of propelling apparatus in proportion to the power 
developed. 
(3) Improvements in the materials used in shipbuilding ; 
better structural arrangements; relatively lighter hulls and 
larger carrying power. 
(4) Improvements in form, leading to diminished resistance 
and economy of power expended in propulsion. 
These general statements represent well-known facts—so 
familiar, indeed, that their full significance is often overlooked. 
It would be easy to multiply illustrations, but only a few repre- 
sentative cases will be taken. 
Transatlantic Passenger Steamers. 
The Transatlantic service naturally comes first. It is a 
simple case, in that the distance to be covered has remained 
practically the same, and that for most of the swift passenger 
steamers cargo-carrying capacity is not a very important factor 
in the design. 
In 1840 the Cunard steamship Arz/annza, built of wood, 
propelled by paddle-wheels, maintained a sea-speed of about 
84 knots. Her steam pressure was 12 lbs. per square inch. 
She was 207 feet long, about 2000 tons in displacement, her 
engines developed about 750 horse-power, and her coal con- 
sumption was about 40 tons’ per day, nearly 5 Ibs. of coal per 
indicated horse-power per hour. She had a full spread of sail. 
In 1871 the White Star steamship Oceanzc (first of that name) 
occupied a leading position. She was iron-built, propelled by 
a screw, and maintained a sea-speed of about 144 knots. 
The steam pressure was 65 lbs. per square inch, and the 
engines were on the compound principle. She was 420 feet 
long, about 7200 tons in displacement, her engines developed 
3000 horse-power, and she burnt about 65 tons of coal per day, 
or about 2 lbs. per indicated horse-power per hour. She carried 
a considerable spread of sail. 
In 1889 the White Star steamer Zex/onzc appeared, propelled 
by twin screws and practically with no sail-power. She is steel- 
built, and maintains a sea-speed of about 20 knots. The steam 
pressure is 180 lbs. per square inch, and the engines are on the 
triple expansion principle. She is about 565 feet long, 16,000 
tons displacement, 17,000 horse-power indicated, with a coal 
consumption of about 300 tonsa day, or from 1°6 to 1°7 Ibs. per 
indicated horse-power per hour. 
In 1894 the Cunard steamship Campania began her service, 
with triple expansion engines, twin screws and no sail-power. 
She is about 600 feet long, 20,000 tons displacement, develops 
about 28,000 horse-power at full speed of 22 knots, and burns 
about 500 tons of coal per day. 
The new Oceanzc, of the White Star Line, is just beginning 
her work. She is of still larger dimensions, being 685 feet in 
length and over 25,000 tons displacement. From the authori- 
tative statements made, it appears that she is not intended to 
exceed 22 knots in speed, and that the increase in size is to be 
largely utilised in additional carrying power. 
The latest German steamers for the Transatlantic service are 
also notable. A speed of 224 knots has been maintained by 
the Kazsex Wilhelm der Grosse, which is 25 feet longer than 
the Campania. Two still larger steamers are now building. 
The Deutschland is 660 feet long and 23,000 tons displacement ; 
her engines are to be of 33,000 horse-power, and it is estimated 
she will average 23 knots. The other vessel is said to be 700 
feet long, and her engines are to develop 36,000 horse-power, 
giving an estimated speed of 234 knots. All these vessels have 
steel hulls and twin screws. It will be noted that to gain 
about three knots an hour nearly 50 per cent. will have been 
added to the displacement of the Zez/onzc, the engine-power 
and coal consumption, will be doubled, and the cost increased 
proportionately. 
Sixty years of continuous effort and strenuous competition on 
this great ‘‘ ocean ferry” may be summarised in the following 
statement. Speed has been increased from 84 to 224 knots ; 
the time on the voyage has heen reduced to about 38 per cent. 
