| Lat. | Sun in ♈ ♎ | Sun in ♋ | Sun in ♑ |
|---|---|---|---|
| 0 | 20000 | 18341 | 18341 |
| 10 | 19696 | 20290 | 15834 |
| 20 | 18794 | 21737 | 13166 |
| 30 | 17321 | 22651 | 10124 |
| 40 | 15321 | 23048 | 6944 |
| 50 | 12855 | 22991 | 3798 |
| 60 | 10000 | 22773 | 1075 |
| 70 | 6840 | 23543 | 000 |
| 80 | 3473 | 24673 | 000 |
| 90 | 0000 | 25055 | 000 |
Those that desire more of the Nature of this Problem, as to the Geometry thereof, would do well to compare the XIII. Prop. Cap. V. of the Learned Treatise, De Calculo Centri Gravitatis, by the Reverend Dr. Wallis, Published Anno 1670.
From this Rule there follow several Corollaries worth Note: As I. That the Æquinoctial Heat, when the Sun comes Vertical, is as twice the Square of Radius, which may be proposed as a Standard to compare with, in all other Cases. II. That under the Æquinoctial, the Heat is as the Sine of the Sun's Declination. III. That in the Frigid Zones when the Sun sets not, the Heat is as the Circumference of a Circle into the Sine of the Altitude at 6. And consequently, that in the same Latitude these Aggregates of Warmth, are as the Sines of the Sun's Declinations; and in the same Declination of Sol, they are as the Sines of the Latitude, and generally they are as the Sines of the Latitude into the Sines of Declination. IV. That the Æquinoctial Days Heat is every where as the Co-sine of the Latitude. V. In all places where the Sun sets, the difference between the Summer and Winter Heats, when the Declinations are contrary, is equal to a Circle into the Sine of the Altitude at six in the Summer Parallel, and consequently those differences are as the Sines of Latitude into, or multiplied by the Sines of Declination. VI. From the Table I have added, it appears, that the Tropical Sun under the Æquinoctial, has, of all others, the least Force. Under the Pole it is greater than any other Days Heat whatsoever, being to that of the Æquinoctial as 5 to 4.
From the Table and these Corollaries may a general Idea be conceived of the Sum of all the Actions of the Sun in the whole Year, and that part of the Heat that arises simply from the Presence of the Sun be brought to a Geometrical Certainty: And if the like could be performed for Cold; which is something else than the bare Absence of the Sun, as appears by many Instances, we might hope to bring what relates to this part of Meteorology to a perfect Theory.
Concerning the Distance of the Fix'd Stars. By the Honourable Francis Roberts, Esq; S. R. S.
THE Ancient Astronomers, who had no other way of computing the Distances of the Heavenly Bodies, but by their Parallax to the Semi-diameter of the Earth; and being never able to discover any in the fix'd Stars, did from thence rightly enough infer, that their Distance was very great, and much exceeding that of the Planets, but could go no farther otherwise than by uncertain guess.
Since the Pythagorean System of the World has been reviv'd by Copernicus, (and now by all Mathematicians accepted for the true one) there seem'd Ground to imagine that the Diameter of the Earth's Annual Course (which, according to our best Astronomers, is at least 40000 times bigger than the Semi-diameter of the Earth) might give a sensible Parallax to the fix'd Stars, though the other could not, and thereby determine their Distance more precisely.
But though we have a Foundation to build on so vastly exceeding that of the Ancients, there are some Considerations may make us suspect that even this is not large enough for our purpose.
Monsieur Hugens (who is very exact in his Astronomical Observations) tells us, he could never discover any visible Magnitude in the fix'd Stars, though he used Glasses which magnified the apparent Diameter above 100 times.