( a6 9 )

sicient to Intercept the Sun, and cast a true Shade, and make the Spaccslarge and fair, though the Heighth and Distance of the Building, and Posi-tion of the Plain, upon which you receive the Shade, and of the Line onwhich you measiirc the Spaces, be not exactly known. But it is convenientthat the Plain on which you take the Shade be not far from Perpendicularto the Sun, at least not very Oblique, and that the Wall which casis theShade, be straight and sinooth at the top, and its Direction nearly East andWesi. The principal Objection is, That the Penumbra, or Partile Shade ofthe Sun is in its Extreams very disiicult to distingurslv from the true Shade,which will render this Obfervation hard to determine nicely. But if the Sunbe transinitted through a Telelcope, aster the manner used to take his Speciesin a Solar Eclipfe , and the upper half of the Object Glaß be cut off by aPaper pasied thereon, and the exact upper Limb of the Sun be seen jusi:emerging out of, or rather continging the Species of the Wall, (the Positionof the Telelcope being regulated by a fine Hair extended fn the Focusof the Eye Glaß) I am affured, that the limit of the Shade may be ob-tained to the utmost Exactncß. I (hall only further advertile, That theWinter Tropick by this Method may be more certainly obtained than theSummer's, by realbn that the fame Gnomon does afford a much larger Ra- -dius for this manner of Obfervation.

XX. I have found it neceflary, to make new Solar Numbers, because Tb<e SoUrin my old, I had neglected. to apply Refractions in all the Altitudes aboveqoDegrees; wherein yet Realbn and forne little Experience hath Ihewedsteed.’me, they are not Insensible. I. found S. C affini' s Observations, which I n - Il °- f- 22 °*took from Rjcciolus his Astonomia 'Reformata-, much more Accurate thanTjcbo's, and therefore sought out Numbers that might anlwer them. TheApogäum I found it necesiary to promote 44 Minutes ; Ib that, Anno In -eunte 1655. it might be in 3. 7 0 . 30'. 00". and to make the greatelfcEquation only 1® 54^ 13". whereby I found, the Phxmmcna would beanlwered much more accurately than I expected, and-as near, allthmgs con-sidered, as I could delire.

But still 1 was uncertain, W’hether the Refractions in the seid Cajßni’sTables were jusi mealures or not, and I had no Conveniencies for ma-king Trial. At Iasi, I thought on this Expedient, which fully sitisfied me ;vi\,

I considered, That if some of those Observations of the Distances of 2"from the © by Day, and from the Stars in the Night preceding or follow-ing, were skiliiully Examined, they might fhew me the true Quantity ofthe Equations of the Sun’s Orb, or rather the Difference of his Mearr andEqual Motion. I turned over his Progymnasmata , and pitehed on two,

The first made, Ann. 15-85. Marcb 5. 4^. 42'. and 7 h . 1 r 1 . Poß Meridianwhereby 1 found, the © at qh. 41'. was 94 0 . 47 s in Antecedence of theLucida Calcis K. The second made, Ann. 1585. Septcmb. iy. yh. i y'.and 6 h . yy'. Manu Wherefrom , (applying and considering the Re-fractions'