660 PHILOSOPHICAL TRANSACTIONS. [aNNO 1683. 



pent up, work more forcibly on each other. And that sounds and tremors 

 may be produced by such heat, though it work only on air, watery vapours, 

 or nitre, included in pores and cavities, appears by several experiments; as 

 that of filling glass bubbles half full with water and nitre, which being set to 

 the heat of the fire, will tremble with a sort of humming sound, and after 

 that break with a great noise and violence. 



The extent of this earthquake was but 70 miles, or thereabouts; its largest 

 distance was from S. E. to N. W. the least from N. to S.; a very inconsider- 

 able space, if compared with that which others have extended, as for instance 

 the earthquake which happened in the south parts of Norway, April 24, 

 Anno 1657, 160 miles in length, and as much in breadth; and Kircher men- 

 tions one of 200 miles in length. 



Another earthquake, far more considerable than the above, on all accounts, 

 happened Oct. 9, about 1 1 at night. It was noticed in Oxfordshire northwards 

 very much, and it spread over all the midland counties, and extended into 

 Derbyshire, in which, as in the coal counties, it was very violent. 



An Account of the Eclipses or Ingresses of Jupiter's Satellites into his Shadow, and 

 such Emersions of them from it, as will be visible at the Observatory at Green- 

 wich in the last three Months of this Year l683. By J. F. Astron. Reg, 

 N°15I, p. 322. 



I here send you an account of the eclipses or ingresses of Jupiter's satellites 

 into the shadow, and such emersions of them from it as will be visible at the 

 observatory in the last three months of this year; they are calculated from new 

 tables which I made this last summer, and I hope so exactly that the ingresses 

 of the first will seldom differ above 5 minutes from the time stated, the 3d but 

 little more : the eclipses of the 4th and 2d I dare not promise you shall agree 

 so well, for I find their motions evidently entangled with inequalities, which it 

 will require a long time and many more accurate observations to determine and 

 limit, than I have yet obtained: these eclipses have been esteemed, and certainly 

 are, a much better expedient for the discovery of the longitude than any yet 

 known, by reason that they happen frequently, and are easily observable with a 

 telescope of 12 feet, or for need with one of 8. These ingresses (and emersions 

 also if visible) from the time till the opposition of the and If. happen truly 

 on the right hand, or in antecedence of the planet, but if they shall be observed 

 with telescopes of only two convex glasses, which invert the object, they appear 

 on the contrary or left side of him. If these find acceptance with our ingenious 



