EXPERIMENTS OF MESSRS. FINCHAM AND RAWSON. 
639 
ments have been conducted. It represents a section of the model; TK is the yard 
by means of which the deflecting weight hanging at Q, deflects the model from the 
upright position. AC is water-line in the upright position, and BD that in the ex- 
treme position into which it rolls ; EF that in the position in which it finally rests. 
In the first place, the model is adjusted by means of moveable weights, until the 
water-line AC is parallel to the upper side, LN, of the model ; and then a string, SK, 
is fixed at S and K, so that when the deflecting weight is placed at Q no effect is pro- 
duced by the deflecting weight on the model until the string SK is cut (RS is a fixed 
beam independent of the model). 
When the string SK is cut there is an extreme deflection where the water-line be- 
comes BD, and a permanent deflection where the water-line becomes EF. 
■■ These lines are determined in the following manner: PX is a thin graduated scale, 
fixed at. P at right angles to the arm of the lever TK, and having a strip of prepared 
paper fixed upon its surface, which shows distinctly, by the depth to which it is wetted 
when the vessel rolls, a point in the extreme position of the water-line. Two other 
points in this position of the water-line are determined by means of scales similarly 
applied to L and N. 
When any two of these three points are observed, a section of the model being 
drawn of the half-size on a drawing-board, we could set off upon it the distances Pp, 
LZ, Nw, and thus draw in the water-line BD. There is no occasion to use prepared 
paper to show the water-lines, excepting in the ultimate deflection. 
The paper which we used, and which answered the purpose admirably, was nothing 
more than common writing-paper rubbed over with a little colouring, in order to take 
off from the surface of the paper any oily matter which might prevent the water’s 
making a distinct mark upon it. 
This means was adopted as the best means, after several other expedients had been 
tried with partial success. 
The centre of gravity G was determined by observing the permanent water-line 
EF in a number of deflections by means of various deflecting weights. The position 
of this water-line, for any given deflecting weight, being set out on the drawing, we 
were enabled, knowing the weight of the vessel, to determine the position of the centre 
of gravity, by well-known principles of statics, with no other aid than that of the 
scale and compasses. Suffice it to say, that great care was taken to get this point. 
The points H and h, which are the centres of gravity of the part immersed in the 
vertical position of the vessel and in the position into which it rolls, were determined 
from the known property of the centre of gravity of a triangle in fig. 1, and from the 
common formula for determining the centre of gravity of the segment of circle in 
fig. 2. 
The drawings were made to half size from the following Table, which was filled 
up during the time the experiments were in operation : this circumstance enabled us 
obtain all the data required for our computations with extreme exactness. 
