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involves very serious difficulties of principle which, however, affect 
the determination of their position forward and aft, rather than 
their height, with which we are now concerned. We may assume 
that in most of the Windermere yachts the centre of pressure is 
from fifteen to twenty feet above the centre of lateral resistance. 
Hence the heeling power of the wind may reach to nearly half a 
ton, acting at the end of an arm fifteen or twenty feet long. We 
evidently require a strong righting couple to counteract a power 
like this. 
It will not be sufficient for safety that the righting power of 
the boat should be ultimately greater than any heeling power that 
can ordinarily be brought to bear upon her; there must be a 
considerable margin. ‘That the righting power should be at last 
overcome by the heeling power is not the only, or indeed the chief, 
danger,—which arises from what we may call angular momentum. 
When a boat is nearly on an even keel, the arm of the righting 
couple is short, and if she then be struck by a squall of moderate 
strength, she will heel over. In doing so she will acquire an 
angular motion, and.this motion will not be at once checked when 
the arm of the righting couple is so lengthened by her heeling over 
as to make the righting force equal to the heeling force. Just asa 
pendulum when let go will swing past the position of equilibrium, 
so will a boat pass the position in which the righting and heeling 
forces would be equal. It is this which makes sudden squalls 
striking a boat when nearly upright so dangerous, it is this which 
constitutes a part of the danger of that moment when a boat has 
just gone about, when of necessity she comes into an upright 
position. On lakes like ours, where with the utmost care a steers- 
man must in the long run be occasionally taken a little by surprise, 
there is no safety but in thoroughly sound principles of construc- 
tion. 
Now the chief safeguard against capsizing is this, that the 
action of the boat in heeling over tends of itself very materially to 
diminish the pressure on the sails. The law of this diminution is 
_ hot quite settled, but according to what seems the most probable 
‘theory, and fairly borne out in practice, we should have the 
