548 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 10. 



The Moon's Eclipse, Feb. 2, 1/10, observed at Streatham, near London, and 

 compared with the Calculation. By the Rev. H. Cressener, M. A. and 

 F.R.S. N°325, p. ]6. 



In the last lunar eclipse, on Feb. 2, 1709-IO, the time of the end I found 

 to be the same very nearly, which the calculation, according to our most 

 learned president's (Sir J. Newton) admirable theory, promised me to expect. 

 There being therefore no examples of any calculation, that I know of, accord- 

 ing to that theory, nor of the theory's agreement with observation, yet made 

 public, I thought it proper to offer this one, that the exact agreement with 

 observation in this, may prompt some of them to try the like in others. I 

 have added the calculation from Mr. Flamsteed's tables, according to Horrox's 

 theory, as published in Mr. Whiston's Astronomical Lectures, with the radixes 

 of the mean motions, corrected according to their first author's later observa- 

 tions, which are the same with those assumed in Sir Isaac Newton's theory. 

 By comparing these two calculations, we may observe, that though most of 

 the additional equations in Sir Isaac Newton*s be very small in this situation 

 of the moon, yet they all conspire so as to make its place considerably more 

 agreeable to observation, than those of Horrox's system. 



The observation was made at Streatham, about 6 miles nearly direct south of 

 London, with a very good 8-foot telescope. To correct the clock, for want 

 of an instrument, I carried with me next day two watches; that were before 

 adjusted to the clock, and compared them with Mr. Flamsteed's at the Royal 

 Observatory, having first noted its error by an observation of the sun's transit 

 of the meridian, communicated to me by his assistant : on my return, I found 

 my watches still agreed together, and with my clock, which proved that they 

 have gone true, and gave me the exact error of my clock, and the true time 

 of observation. Mr. Flamsteed has since been pleased to acquaint me, that 

 by his observation of the meridional transit of the lion's heart, during the 

 eclipse, his clock needed a yet further correction of one minute, which I have 

 here accounted for. 



Feb, 1709-10. 



The mean time of the mean opposition 2d. 4h. Qm. 42s. 



The mean time of the true opposition 2 JO 54 48 



At which the true place of the sun is 10s 24° 55' 50* 



And its equation to be added. 



