Repository: UIHistories Project: War Publications - WWI Compilation 1923 - Article 46 [PAGE 11]

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SECTION B. Definition and Simple Applications of the "mil"—'J he Parallax. A first difficulty which the student will encounn r m artillcr work t in the fact that the U. S. Field Artillery measures angles generally so-called "mils".* The sighting instruments of the gum arc irradunit, instead of degrees, and the tal The mil will therefore hive to hi- ca v course which is to nreoare for arii In the Heavy and Coast Artillery the conventional system of measuring angles in degrees, minutes and seconds is used together with the mil system. It should also be noted that the Field Artillery, which has up to the present measured lengths in yards, is. as far as length measurements are concerned, in a stage of transition, since, in order to agree with French practice, lengths are in the future to be measured in meters. ho one one-thousandth of a radian.** 0 There would thus be 2000.77 = 6283 (approx.) mils in 360 . This would be a very inconvenient unit for numerical computations. The mil actually adopted in the army is the sixteen-hundredth part of a right angle: ' I mil = right angle = .05625° = 1600 "

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360°, 3200 mils = 180°, 1600 mils = 90 about

000

The following is quoted from official instructions of the United X States Army: Definition: All U. S. mobile artillery sights will be graduated clockxvise in mils. A mil is 1-6400 of a circle. The arc which subtends iil at the center of a circle is, for practical purposes, equal to i-iooo tangent are nearly equal f of the radius. The greater than 350 mils.***

^cTmpare for this .ectton: BUhoP. p. 47 «.; Hor**Dmf«*. PP. ''''^J**'*™* mil and parallax; numerou. application, pp. 6a-.3°i Gunnery PP. 33. 34. j8. Manual P P ^ " "According to other text boolc. the - U w a . «*£>%£ arc * . o , J h e J * * * * * between this angle and the angle x-xooo radian if only aooui one ™ •••350 milt = 3SQ . 36o° _

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