An astrological discourse with mathematical demonstrations proving the powerful and harmonical influence of the planets and fixed stars upon elementary bodies in justification of the validity of astrology : together with an astrological judgment upon the great conjunction of Saturn & Jupiter, 1603 / written by that worthy, learned gentleman, Sir Christopher Heydon, Knight ; and now published by Nicholas Fiske ...

CHAP. III. (Book 3)

The second Reason of the foresaid Dif∣ference, drawn from the difference of Ʋnion in the Beams. (Book 3)

SEcondly, In the work of the Stars Union of Beams is a thing regarded, * 1.1 as of special consequence. But it is clear to them that have any insight in the Op∣ticks, that in Winter the Union of the Beam, incident with the Beam reflected, is not comparable with that which the greater Altitude of the Sun causeth in Summer; and therefore the effects de∣pending upon this Union, must accord∣ly be increased or diminished in propor∣tion. That this is true,

[illustration]

Diagram.

Suppose A B in the first Figure, and C D in the second, to be two equal parts of the Earths Superficies; whereupon the Beams of the Sun E A in Winter, and G C in Summer do fall: E A in the Winter Solstice, making an Angle with the plain of the Horizon H A B, of 14. gr: 56′. 30″. viz. E A H, or E B H, be∣ing the Meridian Altitude of the Sun at London upon that day. Likewise let G C K, or G D K, be admitted to irradiate the Earth at the highest Meridian Alti∣tude

in the Summer Solstice at an Angle of 61 gr. 59′. 30″. Then forasmuch as (by the principles of the Opticks) the Angles of incidence and reflection are evermore equal, A F in the first Figure, and C M in the second, being the reflected Beams, E F and G M shall be reverberated from A B and C D at like Angles with their proper incidents. Which being true, it is also evident, that because the inward Angles at C and D are greater then the inward Angles at A and B, the Triangle C L D shall of necessity be greater then the Triangle A I B. And forasmuch as the Union of the Beams, incident with the reflected, hapneth within the limits of these Triangles, therefore of consequence the Union C L D in Summer is so much greater then the Union of A I B in Win∣ter, as the area of the one doth exceed the area of the other, which is about, or rather somewhat above, six to one; and being joyned to the former difference, as is usual in addition of proportions, prov∣eth, that this difference of Union, toge∣ther with the Suns stay in Summer, cau∣seth the heat to exceed that which we re∣ceive in Winter above twelve times.

Notes

• * 1.1

  Union of Beams, what it causeth.