x68

Astronomy.

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happen, which depend on the annuu* — ,j,nrnal Rotation of the Earth , and the .

Revolt

and Spheres and Orreries were now no unc 0 | sl ^' t j||Things; though Orreries bore an excessive P r i c ^ j>yvery lately. The first large one made in Lo^ ^Mr. Rowley was purchased by King George I* 3 g slJ - 1 ,Price of 1000 Guineas; nor has any of that larg®which contains all the Movements of Primat^^eSecondaries, been fold for less than 300 I. at anyfince. , r fiii 5

10. There have been various Forms invented so ^noble Instrument, two of which have principaltain’d, viz. the Hemispherical Orrery , and the ^ 0 ii £Sphere ; though the Orrery at first was made M ^any Sphere, and with only the Sun and the East *!: atMoon revolving about it; but this was too imp er . j, tState, and they soon began to invest it, some ss 1 f 0 tHalf-Sphere , some with a Whole or Compleat Sph^ 1 .* ofotherwise it could not be an adequate Represent^ 1the Solar System. ir>

xi. The Hemispherical Orrery has been tMgreater Numbers than any other, on account o* Abeing made much cheaper and easier than tho* c cSphere of the fame Size ; there being a vast e! y t

between placing an Hemisphere en the Bex of eM fin 1

and disposing an Orrery in a large moveable 'Sphefe ■then the Idea given us by the former is veryand imperfect ; and ’tis surprising to think thpy 11 a d«have such a Run as they had, Mr. Wright having ^ 0 fbetween forty and fifty of that Sort since the jjficMr. Rowley his Master. And though I incline to ^gfew more of that Form will be made, yet as th e ; ^ghad so great a Name, I have thought proper to othe Reader a View of one in a Print.

12. This ill-judged and erroneous Form of an r h

had this Effect with those who knew the Nature ^ lwMachines very well, that some applied themsen^^.!construct Orreries in a Compleat Sphere, others > 0 .^^ ofsuch Instruments as served to exhibit the Mot>°

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