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RABBET to RAISING a purchase
RAKE to RATES
RAKE
RAKING a ship
RANGE
RATES
RATES to To REEVE
RECKONING to RHOMB-LINE
RIBBANDS to RIGGING-OUT a boom
RIGHTING to ROBANDS, or ROPE BANDS
ROGUES-YARN to ROUND-HOUSE
ROUNDING to ROYAL
RUDDER to RUNNING-RIGGING
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RANGE (continued)
Weight, or gravity, always operates equally on a falling body; for as it always subsists in an equal degree, it must perpetually act with equal force, or produce always the same effect in the same time. So if, in the first instant of falling, it communicates to a body a certain force sufficient to move a certain space, it must, in every following instant, communicate a force capable of moving it the like space, and by this means the velocity of a falling body is every moment accelerated; for if it has one degree the first instant, it will have two the second, three the third, and so on. Hence it must move different spaces every instant, and by that means describe the curve-line above mentioned.The line a b, fig. 19. plate VI. is called the extent of the range, or the amplitude of the parabola; and the line a d, the elevation of the mortar.
To make a shell sail on a given place, two things are to be considered; viz. the elevation of the mortar; and the quantity of powder used to charge it; both of which may be ascertained as follows: A shell discharged from a mortar, pointed vertically, will describe a line nearly perpendicular to the horizon: I say nearly, because the mortar will always have some little motion, which will destroy the exact perpendicularity of the shell's flight ; but abstracted from this, a shell, discharged vertically, would fall again into the mortar (Le Blond's Elements of War).
If the mortar be afterwards inclined more and more towards the horizon, the shell will fall still further and further distant from the mortar, till the elevation rests at 45� and the more the mortar is pointed under this angle, the more will the range of the shell be diminished: all of which is strictly demonstrated by geometry. But the following is a very simple manner of conceiving it, without having recourse to that science.
A shell, discharged in the direction of a line, nearly perpendicular to the horizon, will fall at a little distance from the bomb-vessel. This requires no proof. A shell, thrown according to a line that makes a very acute angle with the horizon, will presently come to the ground by its weight, and by consequence will not,, any more than the other, fall at a considerable distance from the mortar.
Hence it is easy to conceive, that in order to fall at the greatest distance from the mortar, the shell must be fired according to an elevation at the greatest possible distance, as well from a vertical, as from an horizontal line. This elevation divides in two equal parts the angle formed by the vertical and horizontal lines, which being of 90 degrees, or what is called a right angle,. a shell will be thrown to the greatest distance, in the direction of a line making an angle of degrees. For above this angle the range will diminish, because the shell approaches the vertical line ; and under the same elevation it will also decrease, because the flight of the shell approaches the horizontal line.
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© Derived from Thomas Cadell's new corrected edition, London: 1780, page 233, 2003
Prepared by Paul Turnbull
http://southseas.nla.gov.au/refs/falc/1040.html