ON STEAMSHIP PERFORMANCE. 12S 
In the case of the ‘ Atrato,’ where the proportion between breadth and draft 
is as 1 :-448, the coefficient would be like H.M.S. ‘ Warrior’ and ‘ Achilles,’ 
or the mean between the two would give -8; and this multiplied by 40-92 
+2 x 18-35=62-09, or ‘71 feet shorter than is actually the case. The cause 
of this is that the ‘ Warrior’ and ‘ Achilles’ both have more rise of floor than 
the ‘ Atrato,’ and this rise of floor may be judged from the coefficient of fine- 
ness of midship section ; therefore, by using a little caution in the use of this 
Table, the girth at the midship section may be found to a very close ap- 
proximation. 
Sarface of skin in square feet... . 0.06 cers an wewe 17233 
This surface has been exactly measured from the lines of the ship ; and 
where this has not been possible, the coefficient of -77 may be judiciously 
used from a comparison with other ships, of which the surface of skin has 
been laid down and calculated, and given at the end of this Report. 
Resistance due to skin equal to the surface of the skin multiplied by the 
square of the speed of the ship, in knots, and the product divided by 100, 
supposing that the skin of the ship is clean and smooth, or 
= 27300 pounds skin resistance. 
Total resistance equal to 15850+427300=43150 pounds. Horse-power 
required for ship’s way equal to the resistance due to ship’s way multiplied 
by the speed of the ship, in feet per minute, and the product divided by 
33000, or 
=546 horse-power for ship’s way. 
Horse-power required for skin-resistance equal to the resistance due to 
skin multiplied by the speed of the ship, in feet per minute, and the product 
divided by 33000, or 
=940 horse-power for skin-resistance. 
Horse-power required for slip equal to the total resistance multiplied by 
the slip, in feet per minute, and the product divided by 3300, or 
=406 horse-power for slip. 
Total horse-power required 546+4940+4406= 1892 
Horse-power expended on engines and propeller .. 2207 —1892—315 
Percentage of total horse-power employed in driving 
eT a Stale At o's 8a hee ile Pema cel 24 
Percentage of total horse-power employed in driving 
(DTS | (GCS A a ale Se a 42 
Percentage of total horse-power expended on slip.. 13 
Percentage of total horse-power expended on engines 
man RCRBUDE RNR voir) 2 go, mt, ou agiiy), 3 14 
Consumption of coals per nominal horse-power, per 
eer. ance a ckcls ro a cee eared 9-9 
Consumption of coals per indicated horse-power, per 
eee AL SA Ae aL os STS be 3°6 
