Description oF A SPRING BLOCK. 337 
to difcharge fo much of its contents that the furface would 
approach the bottom. 
It is evident, that by this method, a ftandard may be 
formed for any length, fuperficies, or capacity, and alfo 
for any weight, if the ipecific gravity of the water made 
ule of be given, 
ca 
| sinshdeniaieiamntienbiciil 
N°. XL. 
Defcription of a SPRING-Biocx, defigned to affift a veffel 
in Sailing. By Francia Hopkinson, Esq. of Phi- 
ladelphia. 
flonoured wiih the Magellanic Gold Medal, by an award 
of the Society, in December, 1790. 
T is an acknowledged fa&, that when the fhrouds 
. of a veflel are braced very tight, fo as to prevent 
the mafts from having any play or fpring, fhe will not 
fail as faft as when her mafts are permitted to bend a lit- 
tle to the impulfes of the wind. ©The reafonis, that the 
wind is feldom uniform in its force for any length of time; 
and itis impoffible that a fudden encreafe of impulfe fhould 
inflantancoufly communicate a proportionable velocity to fo 
heavy a body, placed in a refifting medium of fo great 
denfity. \ 
In fuch cafe the veffel is forcibly prefled into or again 
the water, and is obliged to heel from the blaft, until’a 
progreflive motion, adequate to the force impreffed can 
be communicated to the whole mafs. But thefe fudden 
prefflures againft the water and this heeling of the veffel, 
are great obftacles to fait failing : in as much as they oc- 
Ert.i2 cafion 
