The anatomy of Urania practica: or, a short mathematicall discourse; laying open the errors and impertinencies delivered in a treatise lately published by Mr. Vincent Wing, and Mr. William Leybourne, under the title of Urania practica. By Jeremy Shakerley philomath.

CHAP. IX. A brief summary of some other Defects and Imper∣fections.

BUt my room grows narrow, and so tyeth my Discourse to a period: Good Reader, be pleased to take the rest of my collections in a bundle; I shall onely tell you what it contains, and would, if my professed brevity had granted me leave, have laid open the severall pieces to your view.

First, I s••y, that by our Authors rules, the Sun's al∣titude cannot be gathered universally: for though the Example, pag 99. be truly wrought, yet if we turn to the fixt Book for a precept, we shall finde none, but

onely a few concise Tables, calculated for some latitudes which are too narrow and insufficient for him, whose in∣tentions are for narrow and insufficient for him, whose in∣tentions are for generality and exactnesse.

Secondly, the tedious calculation of the Moons Pa∣ralax in her circle of Altitude, detracts from the praise of the Book, and might have been with far more ease, and by the onely help of the Logarithms supplyed thus. As the Radius to the Sine of the Horizontall Parallax, so the Cosine of the Luminuries altitude, to the sine of the Parallax in that altitude. This way is no lesse de∣monstrative, and far more easie then the other which our Authors have used, pag. 99.

3. That the table of hourly motion of the Moon from the Sun, pag. 118. cannot be exactly true, because it sup∣poseth the Suns motion to be equal, and still of the same quantity; which neverthelesse by reason of his Eccen∣tricity is not so, nor can be affirmed.

4. The herozontall Parallax of the Sun is not still 3. min. o. sec. according to the Paper adjoyned to the end of pag. 118. but if that be his Parallax in his meane di∣stance, the Apogaean Parallax is 2. min. 53. sec. The Pe∣rigaean Parallax 3. min. 7. sec. according to our Authors Eccentricity.

5. I affirme no Eclipse of Sun or Moon can be truly calculated, if we use no other rules then what our Au∣thors have given us. For it appeares not whether they have used any reduction of the Moone from her Orbe to the Eclipticke; or of the Sun from the Ecliptick to the Moones Orbe; either of which wayes (consideratis con∣siderandis) would serve. If they used the first, they finde onely the greatest Obscuration, which is not the midle of the Eclipse. If they used the second, they finde onely the midle of the Eclipse, which is not the greatest Ob∣scuration, Vide Kepl. Astr. Cop. pag. 865.

Thus hath my Pen run over these imperfections which are the principall Moles in the face of Urania Practica,

and that without all hatred or desire of Contradiction; the Causes whereof have no predominance in the least over my affections. I wish my Inke had rather been wa∣ter to have washed a way these blots of Art, then markes to make them notorious. Yet I shall be glad if my Au∣thors can clear themselves hereof, which for the present I see not how it may be done. My wishes are, that God the creator of the stars, and the disposer of their influen∣ces, would second the weake endeavours of me and o∣thers that desire the restauration of these sciences, for the common good of Man-kinde, and the glory of his Name, Amen.