; B L O 
tliey carry, and tile ufes to which they are applied. A 
very confiderable improvement lias been lately made in 
the blocks of Ihips, by Mr. Hopkinfon, of Philadelphia, 
the principles of which are thus explained, in his paper 
on the ('object,, publiftied in the Tranfadtions of the Ame¬ 
rican Philofophieal Society. 
“ It is an acknowledged fa£h, that when the fhrouds of 
a veftel are braced very tight, (o as to prevent the mads 
from having any play or fpring, (lieWill not fail (o fait as 
when her mads are permitted to bend a little to the im¬ 
pulses of the wind. The reafon is, that the wind is fel- 
dom uniform in its force for any length of time, and it is 
impoflible that a fudden increafe of impufe (hould in- 
JlantancovJly communicate a proportionable velocity to fo 
heavy a body, placed in a relifting medium of fo great a 
denlity. In fuch a cafe, the veftel is forcibly prelled into 
or againft the water, and is obliged to-heel from the blaft, 
until a progreftive motion, adequate to the force im- 
prefted, can be communicated to the whole rnafs. But 
thefe fudden preftiires againft the water, and this heeling 
of the veil'd, are great obftacles to faft failing ; inafmuch 
as they occalion an unprofitable expenditure of the force 
which (hould puftt her forward. 
“ When-a velfel firft hoifts her (ails, although five may 
be in a (ituation to receive the full impulfe of the wind, 
llte will not immediately proceed with the velocity which 
fne will afterwards acquire from the fame force ;- having 
not yet got under way, as the feamen exprefs it. Upon 
the fame principle, when a veffel is-failing at the rate of 
five knots, if a fudden blaft of wind (hould come, which 
w'ould enable her to make feven knots, (lie may be con- 
fidered as being perfectly ftationary with refpeft to the two 
additional knots, and will require fome time to get under 
way, as to them. Now the eft'ett produced by relaxing the 
fhrouds is, that the mall, receiving the firft impredion of 
the wind upon the (ails, ads as a fpring, and, yielding to 
the impulfe, gradually communicates motion to the whole 
veffel, occafioning an eafy tranfition from one degree of 
velocity to another; fo that her way is not checked by 
her being fuddenly urged againft the refilling medium, on 
the accellion of every new force imprefled. But the mif- 
fortune is, that the advantageous ttfe of the mad can be 
exereifed only to a (mall extent ; for, if it is allowed too 
much play, it will be in danger of breaking. The ob¬ 
ject of the prefent propofal is, to enjoy the fame benefit 
to a greater extent, and with more fecurity. The marts, 
yards, and rigging, of a (hip, receive the firft impulfes of 
the wind. All thefe are in fome degree elaftic. Every 
twifted rope is a fpiral fpring, and every fpar capable of 
being a little bent. But let us fuppofe that the ropes 
were all compofed of ftraight ftrands, that the marts and 
yards were inflexible, and the fails made of thin -light 
wood : in fuch cafe, the veftel, in failing by the wind, 
would, make but little head-way, whatever the ftiape of 
her bottom might be, but would expend the force of 
the wind in heeling, and (lipping to leeward. If this 
be true, her failing muft be conliderably aflifted by any 
means that (hall increafe the ading fpring of her rigging. 
For this purpofe I have contrived a fpring-blcck, to be 
applied to all fuch parts of the rigging as will admit of 
it with fafety and convenience, and where its operation 
will be moft advantageous; but particularly to the fhcet- 
ropes, and, if pradicable, to the dead eyes, in lieu of 
what are called the chains. For this purpofe let a block 
be made in tlie ufual manner, having a ring or eye at one 
end, to which muft be attached a fpiral fpring, linked at 
Give end to the block, and at the other to the timber-head, 
or place w'here it is to be applied. The fpring muft be 
made of well-tempered fteel, and proportioned in ftrength 
to the fervice it is to perform. Within tIre cavity or pipe, 
formed by the fpiral fpring, there-muft be a chain of fuit- 
able ftrength, called a check-chain, conneded by links to 
the hook and ring of the block. When the fpring is not 
in adion, this chain is (lack ; but when the ipiral fpring 
is extended, by the force of the wind, as far as it can be 
without danger of injury, the cljeck-cliain muft (ben be¬ 
gin to bear, to prevent its farther extenfion, and, if (hong 
enough will be an effedual fecurity againft failure. A 
veftel thus furpiftied will be lefs liable to heel, and will 
receive the impulfes of the wind to better advantage, and 
Tail with a more lively and equable motion, than if rigged 
in the common way.” 
With refiped to tlie conftrudion of rtiivers or pulleys 
for (hips blocks, a great improvement lias been made in 
them by Mr. Walter Taylor, of Southampton, by whole 
invention they are better adapted for the rigging of (hips, 
and other purchafes, than any heretofore in ufe; part of 
which invention may alfo be adapted to the boxes of 
wheel-carriages of all kinds. This invention lias the fanc- 
tion of a patent, which deicribes the improvement to be as 
follows, viz. To bufti, box, coque, or plate, all kinds of- 
rtiivers or pulleys, made of any foit of wood whatfoever, 
with lignum-vitae plank, or pieces of plank, let in on each 
fide of the Olivers, to crofs each other, loas it (hall wear 
on the pin-head, or endway of the grain, inftead of any 
fort of metal ; which kind of bufties, boxes, or coques, 
not only ftrengthen the Olivers or pulleys, but wear much 
better and longer than when the Olivers run on the pin- 
flat or fideway of the grain, as is commonly pradifed ; 
and, t by various experiments, it has been found that they 
wear better than coques now in ufe, and with lefs noife, 
and lefs fridion. Secondly, the Olivers or pulleys for com¬ 
mon u(e, w here lefs purcliafe is required, may be boxed, 
coqued, or plated, with pieces of plank of yew-tree, box, 
holly, and feveral other kinds of wood, fo as it is fixed 
with the' rtiivers or pulleys to wear on the pin-head or 
endway of the grain, as before mentioned. Thirdly, when 
lignum-vitae or other Olivers are worn out at the centre, 
they may be made ferviceable again, the fame as new, by 
new buftiing, boxing, coquing, or plating, them, in the 
manner before mentioned. Fourthly, all the buftiing, 
boxing, coquing, or plating, made of lignum-vitae, or 
other wood, is to be (aliened into the Olivers with (crews, 
or rivets. Fifthly, Olivers or pulleys made of Englifh 
wood, being liable to be affeded by the weather, may be 
rendered more ferviceable by being boiled or (baked jn 
oil, or fait water. Sixthly, the new invention to make 
Olivers or pulleys of cart iron, brafs, or any other kind of 
metal, may be made more ufeful, as follows, viz. the 
rim or groove part of the Olivers is to be made of cud 
iron, brafs, or any other metal, and the Olivers are to 
have fpokes of lignum-vitae, or any other kind of wood, 
crofted at the centre, and fattened to the rims of grooves 
with ferews, or rivets; which fpokes may either be coqued 
with metal or iron at the centre, or fixed fo as the lignum- 
vitae or,other wood fpokes (hall wear or run head or end¬ 
way of tiie grain, The Olivers or pulleys with rims or- 
grooves of cart iron or metal may have new fpokes fixed to 
them, when the old ones are worn out, and will do again 
t!ie fame as new ones, which has never before been prac- 
tifed. Seventhly, Olivers buftied, boxed, coqued, or 
plated, witli wood, as before defended, and (liivers or pul¬ 
leys of call iron, brafs, or other metal, made as before de¬ 
feribed, intended to have great (trains or heavy purchafes, 
may have plates of iron, brafs, or other metal, fixed on 
eacli fide at the centre, to be fc i ' , wed or rived in fuch a 
manner as to jam the wood between the laid plates, and 
thereby render the (liivers more fecure. Eighthly, for tlie 
improvement in boxes of wheels for carriages of all kinds ; 
the boxes are to be made oflignum-vitae, or other wood, to 
wear or run on the axle-tree head or endway of the grain. 
This patent is dated 5th of June 1781, and is therefofe 
expired. 
HorJ'e B LOCK, /! An eminence ufually of ftone, cut 
in fteps or notches, ferving as a help to mount on horfe- 
back. Thele were much in ufe among the ancients, whp 
were unacquainted with ftirrups. The Romans erebled 
them at proper Rations along all their great roads. 
BLOCK (Daniel), an eminent painter, born at Stettin 
in Pomerania, in 1580. 'fie chiefly painted portraits, and. 
had- 
