332 Description or a SPRING-BLOCK. 
cafion an unprofitable expenditure. of the force which» 
fhould pufh her forward. 
When a veflel firft hoifts her fails, although fhe may be: 
ina fituation to receive the full impulfe of the wind, yet 
fhe will not zmmediately proceed with the velocity which 
fhe will afterwards acquire from the fame force: having 
not yet got under way, as the feamen exprefs it. Upon 
the fame principle, when. a. veflel is. failing at the rate of 
five knots, if a fudden blaft of wind fhould come, which. 
would enable her to make feven knots, fhe may be confi-. 
dered as being perfeQly ftationary with refpe&t to the two 
additional knots, and will require fome time to get under 
way as to them. Now the effect produced by relaxing 
the fhrouds is, that the maft, receiving the firft impreffion 
of the wind upon the fails, ats as a fpring, and yielding 
to the impulfe, gradually communicates motion to the 
whole veflel, giving her time to get under way, and oc-. 
cafioning an eafy tranfition from one degree of velocity 
to another: fo that her way is not checked by her being 
{fuddenly urged againft the refifting medium on the accef- 
fion of every new force imprefled.. 
But the misfortune is, that this advantageous ufe of the 
matt can. be exercifed only toa {mall extent; for, if it is 
allowed too much play, it willbe in danger of breaking. 
The object of the prefent propofal is to enjoy the fame 
benefit to a greater extent and with more fecurity.. 
The mafts, yards and rigging of a fhip receive the firft 
impulfes of the wind. All thefe are in fome degree elaftic: 
Every twifted rope is a {piral {pring, and every {par capa- 
ble of being alittle bent. But let us fuppofe that the 
ropes were all compoted of ftraight ftrands, that the mafts 
and yards were inflexible, and the fails made of thin light 
wood; in fuchcafe, I fuppofe, that the veffel in failing: 
by the wind would make but little head-way, whatever: 
the-' 
