A handy-book of forensic medicine and toxicology / by W. Bathurst Woodman and Charles Meymott Tidy.

Date:: 1877

Credit: A handy-book of forensic medicine and toxicology / by W. Bathurst Woodman and Charles Meymott Tidy. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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$Multiply the cube of its diameter by 2, and divide by 9, and the quotient will give the weight in pounds. E. g. The weight of a leaden ball of five inches diameter is required. Then 5x5x5 = 125 = cube of diameter. Then 125 x 2-i-9 = 250—0 = 2 71 lbs. 2. To find the weight of an iron-ball from its diameter. Cube the diameter, multiply by 9, and divide by 04; the result is the required weight in pounds. Bequired the weight of an iron ball of 5 inches diameter 1 5x5x5 = 125 ; and 125 x 9-i-G4 = 17^1bs. These rules do not apply to elongated shot (cylindro-conoidal, Ac.), which are now chiefly used. For example, a 4i-pounder gun will fire a 9-pounder shot on the new principles. The weight depends, of course, on how many diameters the balls are in length. Such questions, how- ever, seldom enter into medicaljurisprudence. We shall, therefore, before entering on the consideration of the pecu- liarities of gunshot and other wounds from fire-arms, proceed to discuss briefly— The General Theory of Projectiles, and the Practical Laws of Gunnery. We must premise that a bullet in motion is subject to the ordinary laws of gravity, to the resistance of the air, and to what are often called the Newtonian laws of motion, from their being found in Book I. of the “ Principia.” [They were, however, contained in Des Cartes’ “ Principia Philosophic,” part ii., pp. 38, 39, and 40, published before Newton’s “ Principia.”] Briefly stated, these laws are as follows :— Law I. Every body perseveres in its state of rest or uniform motion [in a straight line~\, unless it is compelled to change that state by forces impressed thereon. Hence a ball from a cannon, or a bullet from a gun, would not deviate from its first direction, or tend to the earth, if the action of gravity and the resistance of the air did not alter and retard its motion. The same may be said of an arrow, of a stone thrown from a sling, of the boomerang used in Australia, of a spear thrown by hand, ifcc. This first law is sometimes called the law of inertia, and expresses the entire indifference of matter to motion or rest. The idea, however, that all matter has a tendency to rest appears to be a common error. For in vacuo [and our vacuums are never perfect] a pendulum, only resisted by the stiffness of the thread which suspends it, will swing all day; and a top, retarded only by the friction of its point, will spin for hours. How long the planetary motions have continued we can scarcely hope to know, though Sir William Thompson believes that for our solar system the matter admits of being determined with at least approximate accuracy, and that it is far from being the eternity of ages which some materialists assert. When a body is moving uniformly—that is, when it passes over equal spaces in equal times—we may define its velocity or speed, as the space passed over in one second (of ordinary time). The law may be written in the form of V = when s is the space or distance moved over uniformly with the velocity V in the time t. The law is true, no matter how short the time may be ; thus, if a body moves uniformly through the space of 0'24 foot in O'OOl second, its velocity is O'fll-f-O'OOl, or 240 feet per$