Agricola, Georgius
,
De re metallica
,
1912/1950
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when it is necessary. </
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<
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>The wooden handle is seven palms long, or even longer,
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in order that it may extend outside; one-half of this handle, two palms
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wide and one thick, is glued to the end of the board and fastened with pegs
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covered with glue; the other half projects beyond the board, and is rounded
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and seven digits thick. </
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<
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>Besides this, to the handle and to the board is fixed
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a cleat two feet long, as many palms wide and one palm thick, and to the under
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side of the same board, at a distance of three palms from the end, is fixed
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another cleat two feet long, in order that the board may sustain the force
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of distension and compression; these two cleats are glued to the board, and
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are fastened to it with pegs covered with glue.</
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<
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>The lower bellows-board, like the upper, is made of two pieces of pine
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and of two strips of linden wood, all glued together; it is of the same width
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and thickness as the upper board, but is a cubit longer, this extension being
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part of the head of which I have more to say a little later. </
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>This lower bellows
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board has an air-hole and an iron ring. </
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>The air-hole is about a cubit distant
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from the posterior end, and it is midway between the sides of the bellows
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board, and is a foot long and three palms wide; it is divided into equal
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parts by a small rib which forms part of the board, and is not cut from it;
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this rib is a palm long and one-third of a digit wide. </
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>The flap of the air
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hole is a foot and three digits long, three palms and as many digits wide;
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it is a thin board covered with goat skin, the hairy part of which is turned
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toward the ground. </
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>There is fixed to one end of the flap, with small iron
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nails, one-half of a doubled piece of leather a palm wide and as long as the
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flap is wide; the other half of the leather, which is behind the flap, is twice
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perforated, as is also the bellows-board, and these perforations are seven
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digits apart. </
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<
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>Passing through these a string is tied on the under side of the
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board; and thus the flap when tied to the board does not fall away. </
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<
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>In this
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manner are made the flap and the air-hole, so when the bellows are distended
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the flap opens, when compressed it closes. </
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<
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>At a distance of about a foot
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beyond the air-hole a slightly elliptical iron ring, two palms long and one
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wide, is fastened by means of an iron staple to the under part of the bellows
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board; it is at a distance of three palms from the back of the bellows. </
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<
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>In
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order that the lower bellows-board may remain stationary, a wooden bolt is
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driven into the ring, after it penetrates through the hole in the transverse
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supporting plank which forms part of the frame for the bellows. </
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<
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>There are
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some who dispense with the ring and fasten the bellows-board to the frame
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with two iron screws something like nails.</
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>The bows are placed between the two boards and are of the same length
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as the upper board. </
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<
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>They are both made of four pieces of linden wood three
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digits thick, of which the two long ones are seven digits wide at the back and
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two and a half at the front; the third piece, which is at the back, is two
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palms wide. </
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<
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>The ends of the bows are a little more than a digit thick, and are
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mortised to the long pieces, and both having been bored through, wooden
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pegs covered with glue are fixed in the holes; they are thus joined and glued
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to the long pieces. </
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<
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>Each of the ends is bowed (
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arcuatur
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) to meet the end of
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the long part of the bow, whence its name “bow” originated. </
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<
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>The fourth </
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