. The encyclopædia of geography: comprising a complete description of the earth, physical, statistical, civil, and political. But if P O, P 0 are not tangents, draw P O and P 6 tangents to the circle O E o, and fi-omC the centre draw C O, C d to the points of contact: draw also the vertical lines C Z andC Z through O and o the places of the observers, and produce P O, P o to meet C O, C din B and D. Now, for the sun and planets the angle O P o is very small, and even for themoon it is not very considerable. The distance P C may tlierefore be regarded, in everycase, as much greater than C O, or
. The encyclopædia of geography: comprising a complete description of the earth, physical, statistical, civil, and political. But if P O, P 0 are not tangents, draw P O and P 6 tangents to the circle O E o, and fi-omC the centre draw C O, C d to the points of contact: draw also the vertical lines C Z andC Z through O and o the places of the observers, and produce P O, P o to meet C O, C din B and D. Now, for the sun and planets the angle O P o is very small, and even for themoon it is not very considerable. The distance P C may tlierefore be regarded, in everycase, as much greater than C O, or C 6. Hence the lines C O, C B, C D may without sen-sible error be considered as proportional to the angles C P O, C P B, C P D ; so that wenave ZCPO: ZCPO = CO: CB and ZCPO: ZCPo = CO: CD; where-fore ZCPO: Z C P O + Z C P o or Z O P o = C O: C B + C D But the angles Angle at the Sun = 17 Mercury- ^ 28 Venus = 62 Mars = 42 Jupiter =: 4 Saturn = 2 88 PRINCIPLES OF GEOGRAPHY. Paiit U. at B and D are very nearly right angles, and therefore, to radius C O, we have C B =Sin C O B = Sin. P O Z; and C D = Sin. C o D = Sin. P o
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