. The encyclopædia of geography: comprising a complete description of the earth, physical, statistical, civil, and political. roduce E D to meet S M in C. Because DAEis a section of that hemisphere of the moon which is turned towards the earth, the visualray O M m is perpendicular to D E: hence the angles m M C, M C m are together equalto two right angles. But because C A is perpendicular to A B, the angles ABC and A C B(or M C m) are also together equal to two right angles: whence it is evident that the anglem M C is equal to A B C; and that the triangles A INI r, A B n are similar. We have,
. The encyclopædia of geography: comprising a complete description of the earth, physical, statistical, civil, and political. roduce E D to meet S M in C. Because DAEis a section of that hemisphere of the moon which is turned towards the earth, the visualray O M m is perpendicular to D E: hence the angles m M C, M C m are together equalto two right angles. But because C A is perpendicular to A B, the angles ABC and A C B(or M C m) are also together equal to two right angles: whence it is evident that the anglem M C is equal to A B C; and that the triangles A INI r, A B n are similar. We have, A r X A B therefore. An: A B = A r: AM. Hence A ]\I = -. • A n Now, A r is the projection of A M on the lunar disc, and will be found by measuring,with the micrometer, in a direction perpendicular to a line joining the horns of the moon, the distance of the illuminated summit M from the enlightened disc at A: also -7-^^ Sin. ° A B Z A B C, radius being unity, the angle A B C is equal to S M m the moons distance or A r elongation from the sun: wherefore we obtam A M = h^ ^j p—> a given quantity. 9 * m. e onga ion.
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Keywords: ., bookcentury1800, bookdecade1840, bookpublisherphiladelphialeaand
