852 . RiPoRT—1899, 
ocean navigation sixty years hence. Radical changes may well be made within 
that period. Confining attention to the immediate future, it seems probable that 
the lines of advance which I have endeavoured to indicate will remain in use. 
Further reductions may be anticipated in the weight of propelling apparatus and 
fuel in proportion to the power developed; further sayings in the weight of the 
hulls, arising from the use of stronger materials and improved structural arrange- 
ments; improvements in form; and enlargement in dimensions. If greater draughts 
of water can be made possible, so much the better for carrying power and speed. 
For merchant vessels commercial considerations must govern the final decision; tor 
warships the needs of naval warfare will prevail. It is certain that scientific 
methods of procedure and the use of model experiments on ships and propellers 
will become of increased importance. 
Already avenues for further progress are being opened. For example, the use 
of water-tube boilers in recent cruisers and batileships of the Royal Navy has 
resulted in saving one-third of the weight necessary with cylindrical boilers of the 
ordinary type to obtain the same power, with natural draught in the stokeholds. 
Differences of opinion prevail, no doubt, as to the policy of adopting particular 
types of water-tube boilers; but the weight of opinion is distinctly in favour of 
some type of water-tubé boiler in association with the high steam pressures now in 
use. Greater safety, quicker steam-raising and other advantages, as well as 
economy of weight, can thus be secured. Some types of water-tube boilers would 
give greater saving in weight than the particular type used in the foregoing com- 
parison with cylindrical boilers. 
Differences of opinion prevail also as to the upper limit of steam pressure which 
can with advantage be used, taking into account all the conditions in both engines 
and boilers, From the nature of the case, increases in pressure beyond the 16U to 
180 lbs. per square inch commonly reached with cylindrical boilers cannot have 
anything like the same effect upon economy of fuel as the corresponding increases 
have had, starting from a lower pressure. Some authorities do not favour any 
excess above 250 lbs. per square inch on the boilers; others would go as high as 
300 Ibs., and some still higher. 
Passing to the engine-rooms, the use of higher steam-pressures and greater 
tates of revolution may, and probably will, produce reductions in weight com- 
pared with power. The use of stronger materials, improved designs, better balance 
of the moving parts, and close attention to details have tended in the same direc- 
tion without sacrifice of strength. Necessarily there must be a sufficient margin 
to secure both strength and endurance in the motive power of steamships. Existing 
arrangements are the outgrowth of large experience, and new departures must be 
carefully scrutinised. 
The use of rotary engines, of which Mr. Parsons’s turbo-motor is the leading 
example at present, gives the prospect of still further economies of weight. Mr. 
Parsons is disposed to think that he could about halve the weights now required 
for the engines, shafting, and propellers of an Atlantic liner while securing proper 
strength and durability. If this could be done in association with the use of 
water-tube boilers, it would effect a revolution in the design of this class of vessel, 
permitting higher speeds to be reached without exceeding the dimensions of existing 
ships. 
It does not appear probable that, with coal as the fuel, water-tube boilers will 
surpass in economy the cylindrical boilers now in use; and skilled stoking seems 
essential if water-tube boilers are to be equal to the other type in rate of coal 
consumption, The general principle holds good that as more perfect mechanical 
appliances are introduced, so more skilled and disciplined management is required 
in order that the full benefits may be obtained. In all steamship performance the 
“human factor’ is of great importance, but its importance increases as the appli- 
ances become more complex. In engine-rooms the fact has been recognised and 
the want met, There is no reason why it should not be similarly dealt with in 
the hoiler-rooms. 
Liquid fuel is already substituted for coal in many steamships. When suffi- 
cient quantities can be obtained it has many obvious advantages over coal, 
reducing greatly manual lahour in embarking supplies, conveying it to the boilers 
