VOL. Xril.] PHILOSOPHICAL TRANSACTIONS. 55/ 



ference between the spring and neap-tides, that is here observed in the river 

 Thames. 



I could easily have made and given you a table for this reduction, if I dare 

 have relied on the account our mariners give of the tides in other ports; but 

 I find their opinions different, except where they have copied from each other 

 in their calendars; by reason of the afore-mentioned difference between the 

 times of the moon's southings and the true high-waters; for which reason I 

 forbear it, till further experience shall have informed us better. 



An Observation of the Beginning of the Lunar Eclipse which happened Aug. 1 9, 

 168I, in the Morning, made on the Island of St. Lawrence or Madagascar. 

 By Mr. Thomas Heathcot, and communicated hy Mr. Flamsteed. N° 143, p, 15. 



Mr. Heathcot was surgeon to a ship, which lay then at the bottom of a deep 

 bay, on the western shore of the island, and that part which the Portuguese 

 and our maps call the Terra del Gada. He had a quadrant of 2 feet radius, 

 and a telescope of Q feet, but no clock ; to supply which defect, he made a 

 pendulum of a string and a bullet SQ inches long, that each single vibration 

 might answer a second of time ; waiting the beginning of the eclipse with his 

 glass, as soon as he saw the true shadow enter on the moon's limb, he caused 

 his friends, who assisted him, to make the pendulum vibrate, and count its vi- 

 brations; of which they had numbered 140, or 2™ 20' of time when he took 

 the height of Procyon, then east of the meridian, 25° 39'; the next day he 

 observed the sun's meridional height with the same quadrant, whence he found 

 the latitude of that place 19° 29' south; hence the time when he took the 

 height of Procyon is found 4^ 51"" morn, and subtracting the 2"* 20^ past since 

 the observed beginning of the eclipse, it gives, for 



The true beginning of the eclipse. . . . , 4^ 



Which at the observatory here I noted at . 1 



Therefore this part of Madagascar is more easterly .... 2 

 or 44° 30', which our maps make 52°, that is 7-|^° more remote from it than it 

 really is. 



Observations made at Dantzic, of the Comet which began to appear there, 

 Aug. J 6, l682. By M. Hevelius. N° 143, p. 16. 

 Of the late comet, I have obtained many of the meridian altitudes, and 

 distances from the fixed stars. But it would be tedious to mention all these, 

 neither have I now time to submit them to a strict calculation. At present it 

 may suffice to observe, that the comet was first seen here at Dantzic, Aug. 25, 



