VOL. I.] PHILOSOPHICAL TRANSACTIONS. 115 



To prevent the water from rising and falling with an undulation, it will be 

 proper that the hole by which the water enters be less than half the bore of the 

 pump. 



The particular observations to be made may be as follows : 



1 . The degrees of rising and falling of the water every quarter of an hour, or 

 as often as may be, from the periods of the tides and ebbs; to be observed night 

 and day for two or three months. 



2. The degrees of the velocity of the motion of the water every quarter of 

 an hour, for some whole tides together ; to be obsened by a second pendulum 

 watch, and a log fastened to a line of about 50 fathoms wound about a wheel. 



3. Exact measures of the heights of every highest tide and ebb, from one 

 spring tide to another, for some months, or rather years. 



4. The exact heights of spring tides and spring ebbs for some years together. 



5. The direction of the wind at every observation of the tides ; the times of 

 its changes, and the degrees of its strength. 



6. The state of the weather as to rain, hail, mist, haziness, &c. and the times 

 of its changes. 



7. At the times of observing the tides, the height of the thermometer, the 

 baroscope, and the hygroscope ; the age of the moon, and her azimuths and her 

 place; also the sun's place. 



A7i Account of several Books lately published. N° 17, p- 301, &c. 



I. Johannis Hevelii Descriptio Cometae, Anno JErsd Christianae MDCLXV 

 exorti; una cum Mantissa Prodromi Cometici, Observationes omnes prions 

 Cometae MDCLIV, ex iisque genuinum motum accurate deductum, cum Notis 

 et Animadversionibus, exhibens. 



This book undertakes to give an account of the second of the two late comets, 

 which appeared when the other was scarce extinct ; concerning which, the au- 

 thor assigns both its true place and its proper motion ; adding a fair delinea- 

 tion of its course, with the genuine representations of its head and train, in 

 each day of its appearing ; and subjoining a general description of some of its 

 more remarkable phaenomena. It was observed at Dantzick by the author from 

 April 6, half past one in the morning, till April 20, at three in the morning. 

 During which time it went with a moderate velocity, making 46 deg. in its orbit, 

 according to the order of the signs, moving from the breast of Pegasus towards 

 the head of Andromeda, and the left horn of Aries ; having, as it is presumed, 

 taken its rise from above Sagittary, and run through the breast of Antinous, 

 under Aquila and the Dolphin to the said Pegasus, and so on, as is already 

 expressed. 



p 2 



