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Extraff of Monfteur Chriftian Hugens de Zulichem his Leh 
ter to the Publijher , efthe i gtb. cj May 1 674. from Paris, 
touching his thoughts of i!Mr. Hook'^ Obfervations for 
provirtgthe ^jMiotionof the Bart h ^ not long fince printed hy 
^j^Wr.Martyn^ mi taken notice of in Numb. \oi,of thefe 
Traifs. 
^^^^'nr^He Obftrvationsof Mr.fli?i?/t for finding out the 
J_ Motion of the Earth are very good, and of great 
confequence 5 but they muft be continued, to fee , whether in 
the courfe of one or more years the Parallaxes do regularly 
anfwer to the Annual Motion of the Earth. To which we alfo 
ftall contribute our labors^ and the Vault,that is in our Obfer- 
vatory, being 28 fathom deep, will in time be very ufeful for 
that purpofe. This, if it fucceed, will prove an almoft entire 
conviflion of the jinti Copernicans^ fince there wil 1 remain for 
them nothing but this un-grounded fubterfuge, to fay, that the 
Center of the Sphere of the Fix't Stars continually changes 
its place for an Annual Motion. 
An Extraft of another Letter , written by Signor Caffini to the 
Publiiher, relating to the fame fubjedljdated June^ 28. 1^74: 
Which weihall infcrt here in the fame language, 'twas writ- 
ten in. • 
NOn foterat^ meo judicio^ D. Hookius aptiori nsethodo 
Parallaxes Orhis annui in Fixis invejligare, nec 
apt tor em ad earn invefiigationem eltgere Stellam^qu£ ex lucidiori* 
ius & verticiproxima e^et, & i polo Zodiaci non rtmota, Nec in- 
milis fuit viridoliifftmi condtus^ cum diver fit at em inveneritdd 
earn partem^ ad quam exigit Paralkxis. 
N^ofir£ equidem Ohfervationes nihil adhuc adeo liquidum hoc 
ingencre exhihuere^ ImtinPixarum jiltitudinihus meridianis, 
variis anni temporihm^ deprehenderemus differentiae alias ah iis, 
qu£ ad promotionemVixarum ex ^yEquimUiorumprMelfione con- 
fequuntur. Nondum tamen , quas ad ham rem pr^meditatifn* 
mm Ohfervationes^ exequipotuimuS'» 
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