1depth
there must be deducted half a fathom, two palms, one and a half digits
and the fifth part of half a digit. But if the tunnel has been driven to a
point where it is under the shaft, then to reach the roof of the tunnel the
shaft must still be sunk a depth of eleven fathoms, two and a half feet, one
palm, two digits, and four-fifths of half a digit.
and the fifth part of half a digit. But if the tunnel has been driven to a
point where it is under the shaft, then to reach the roof of the tunnel the
shaft must still be sunk a depth of eleven fathoms, two and a half feet, one
palm, two digits, and four-fifths of half a digit.
If a minor triangle is produced of the kind having three unequal sides,
then the sides of the greater triangle cannot be equal; that is, if the first
side of the minor triangle is eight feet long, the second six feet long, and the
third five feet long, and the cord along the side of the greater triangle, not
to go too far from the example just given, is one hundred and one times
eight feet, that is, one hundred and thirty-four fathoms and four feet, the
distance which lies between the mouth of the tunnel and the bottom of the
shaft will occupy one hundred times six feet in length, that is, one hundred
fathoms. The distance between the mouth of the shaft and the bottom of the
tunnel is one hundred times five feet, that is, eighty-three fathoms and two feet.
And so, if the tunnel is eighty-five fathoms long, the remainder to be driven
into the mountain is fifteen fathoms long, and here, too, a correction in
measurement must be taken from the depth of the shaft and added to the
length of the tunnel; what this is precisely, I will pursue no further, since
everyone having a small knowledge of arithmetic can work it out. If the
shaft is sixty-seven fathoms deep, in order that it may reach the bottom of
the tunnel, the further distance required to be sunk amounts to sixteen
fathoms and two feet.
then the sides of the greater triangle cannot be equal; that is, if the first
side of the minor triangle is eight feet long, the second six feet long, and the
third five feet long, and the cord along the side of the greater triangle, not
to go too far from the example just given, is one hundred and one times
eight feet, that is, one hundred and thirty-four fathoms and four feet, the
distance which lies between the mouth of the tunnel and the bottom of the
shaft will occupy one hundred times six feet in length, that is, one hundred
fathoms. The distance between the mouth of the shaft and the bottom of the
tunnel is one hundred times five feet, that is, eighty-three fathoms and two feet.
And so, if the tunnel is eighty-five fathoms long, the remainder to be driven
into the mountain is fifteen fathoms long, and here, too, a correction in
measurement must be taken from the depth of the shaft and added to the
length of the tunnel; what this is precisely, I will pursue no further, since
everyone having a small knowledge of arithmetic can work it out. If the
shaft is sixty-seven fathoms deep, in order that it may reach the bottom of
the tunnel, the further distance required to be sunk amounts to sixteen
fathoms and two feet.
A TRIANGLE HAVING A RIGHT ANGLE AND THREE UNEQUAL SIDES.
The surveyor employs this same method in measuring the mountain,
whether the shaft and tunnel are on one and the same vein, whether the vein
is vertical or inclined, or whether the shaft is on the principal vein and the tunnel
on a transverse vein descending vertically to the depths of the earth; in the
latter case the excavation is to be made where the transverse vein cuts the
vertical vein. If the principal vein descends on an incline and the cross-vein
descends vertically, then a minor triangle is created having one obtuse angle or
all three angles acute. If the minor triangle has one angle obtuse and the two
sides which are the second and third are equal, then the second and third
sides of the major triangle will be equal, so that if the first side of the minor
triangle is nine feet, the second, and likewise the third, will be five feet. Then
the first side of the major triangle will be one hundred and one times nine
feet, or one hundred and fifty-one and one-half fathoms, and each of the
other sides of the major triangle will be one hundred times five feet, that is,
eighty-three fathoms and two feet. But when the first shaft is inclined,
whether the shaft and tunnel are on one and the same vein, whether the vein
is vertical or inclined, or whether the shaft is on the principal vein and the tunnel
on a transverse vein descending vertically to the depths of the earth; in the
latter case the excavation is to be made where the transverse vein cuts the
vertical vein. If the principal vein descends on an incline and the cross-vein
descends vertically, then a minor triangle is created having one obtuse angle or
all three angles acute. If the minor triangle has one angle obtuse and the two
sides which are the second and third are equal, then the second and third
sides of the major triangle will be equal, so that if the first side of the minor
triangle is nine feet, the second, and likewise the third, will be five feet. Then
the first side of the major triangle will be one hundred and one times nine
feet, or one hundred and fifty-one and one-half fathoms, and each of the
other sides of the major triangle will be one hundred times five feet, that is,
eighty-three fathoms and two feet. But when the first shaft is inclined,