216 REPORT—1858. 
To this paper are appended Forms of Returns intended to further this object. 
2 
Considering the formula R = AW x = to be the foundation of all sound induc- 
tion on the question of resistances, the author considers also that at present its 
limit of application is to the mid-section only, irrespective of hull, masts, and rig- 
ging, and to the resistance in smooth water with calm weather. 
There are modifications of this equation to meet the increased resistance arising 
from hull, masts and rigging, wind and sea, and the form of the vessel. 
But these modifications embrace only a very small range of the additional elements, 
because no properly-conducted experiments have been made under varied conditions 
at sea. 
The resistances of sections which have come within the author’s observation are 
comprised within the expressions— 
SV? SV? 
—— and 
3582 3219, 
and the specific resistances due to the forms of vessels lie within 6 and 13 per cent. 
of R. 
The following are the results of performance at the measured mile of the Duke of 
Sutherland's yacht, Undine, in July 1856, and July 1858 :— 
1856. 1858. 
Ft. In. Ft. In. 
Screw diameter .......+.. dee tee eters ale Gel eae 7 10 
Ses ee as ee eee 1 Eee 
“p wa Onan aisherpeticres ae & atigvahat seers = Laos 1 4 
Dratt forwards. .c..jics wats sieeve waters thew St Scleas ote 8 6 
Jo dedltrele siete sas cis sie hansacks vee cher cd B- a soe tO 
Sq. ft Sq. ft 
Mid-section...... tatty au Oieisksioie siete : 148. 154 
Indicator Horse-power mace Sistas 162 157 
Knots. Knots. 
Peed! sis sejas b1.0% 45 Aoi Dome asteiel ee BOO meres 9°26 
INo.vof revolations x. Aiotclerisrereresrevels -. 108°00 .... 108°74 
Lip per CENteee psn, aspale stele iagh ais, olstoteia ors 20°52 22.08 17°9 
Now, the first observation that may be made is, that the larger diameter of course 
produced a greater thrust, and so a better result. But this does not follow. 
It will be observed that the pitch is considerably less in proportion to the diameter 
in the new screw. 
The slip was calculated beforehand, and was given to Lord Stafford, a fortnight 
before the trial, as about 173". 
It will be seen that the mean average at the trials was 17°9 per cent. On the 
same grounds, then, that he calculated the slip of the Undine, the author expressed 
the opinion respecting the Ratiler. 
The mean of trials in Yarmouth Roads, under favourable conditions, gives a slip 
of 15°798 per cent. when the Raétler’s draft of water was about 12 feet 4 inches, 
her section 300 square feet, and speed 8:8 knots. A trial in the Thames, in October 
1851, with a mean draft of 13°94 inches, a section of 338 square feet, and a 
speed of 9°141 knots, gives a slip of 17°18 per cent. 
The screw duly adjusted to the form of the Ratéler would make a slip of about 
12 per cent. 
The nature of the slip of the screw may be illustrated by the apparent effect upon 
it when the vessel is moving in a tide-way. 
Out of the seven trips made by the Undine, at the measured mile, the two greatest 
extremes are selected, viz. :— 
Against Tide. With Tide, 
Knots. Knots. 
Speed of screw........... Si blaticucaithc 10°94 .... 10°64 
Dos vessel s scwibngt hectare oe cle ee 7°32- see 10°24 
Slip pex/centsiieuhin siewie ae ate silt ie othe dlc: pS OD iaiiatennn ann 
Revolutions: 2% Jai e wisicleeie's tamcnede . /698"°6)' ¥ .. ann) 90:89 
seleels lett LAG32 he sae okiod: 
