VOL. XXII.] PHILOSOPHICAL TRANSACTIONS. gSQ 



Rother, from the north side of the island, wheeled about by the south side to 

 that eastern corner, and thence by the channel to Rye. 



While things were in this state, divers moorish or marsh lands, adjoining to 

 the river Rother, were often in danger on great rains of being overflowed. But 

 so it once happened, that this drowned land had unexpectedly in one night's 

 time, or little more, discharged itself on another level, somewhat lower than 

 itself. On which indication it was thought advisable, by cutting that isthmus 

 to allow those waters on the north side of the island a straighter passage toward 

 Rye : and to let those lower grounds lie for some time under water, till by in- 

 tromilting the tide, they might be somewhat heightened and then timely reco- 

 vered. In order to which, commissions of sewers have ever since, from time 

 to time, been issued out for that purpose ; and the work, in good measure 

 effected, though not quite finished. 



Of the Invention and Improvement of the Mariner s Compass. By Dr. IVallis. 



N°'276, p. 1035. 



It is not agreed on where, or by whom, the mariner's compass was first 

 invented. I have guessed it to have been an English invention, not only be- 

 cause we have been long conversant in navigation, but even from the name 

 compass, which is used in England ; I am sure it was wont to be so used in Kent 

 when I was a youth, for what we otherwise call a circle. And I take it to be an 

 old English word in that sense, though now, in imitation of the French, the 

 word circle be more common. I know not whether a compass, or any word 

 like it, be so used for a circle in any other language ; but rather cercle in 

 French, circhio in Italian, circulo in Spanish, or some other word derived from 

 the Latin circulus. And from hence the circulus nauticus may come to be 

 called the mariner's compass, which name, being given it by the first inventors, 

 might give occasion for like names in other languages ; as compas, compasso, 

 zee-kompas, &c. Indeed the circinus, or instrument by which we describe a 

 circle, called by us a pair of compasses, may have some like name in other lan- 

 guages ; but how anciently I do not know, nor that a circle absolutely consi- 

 dered other than this circulus nauticus is so called. How far this conjecture, 

 from the name, may give us a title to the invention, till a better appears, I 

 shall not determine, but only suggest to consideration. 



I think it is now agreed on all hands, that what we called the variation of 

 the variation is an English discovery, of Mr. Gellibrand, if I mistake not, one 

 of Sir Thomas Gresham's professors at Gresham College, about the year l()25. 

 That is, that the magnetic needle, in its horizontal position, does not retain the 

 same declination or variation from the true north, in the same place, at all 



