Page:Philosophical Transactions - Volume 001.djvu/149

 they please, and the weight of the Vial full of water taken exactly at every time, and recorded, marking withall the degree of Latitude, and the day of the Month: And that as well of water near the Top; as at a greater Depth.

I have received an Account from very good hands, That on the 26th of September last, at half hour after seven of the Clock, was seen, both in Holland and in France (by curious Observers, with very good Telescopes) the shadow of one of the Satellites of Jupiter, passing over his Body. One of those small Stars moving about his Body (which are therefore called his Satellites) coming between the Sun and it, made a small Eclipse, appearing in the Face of Jupiter as a little round black Spot. The Particulars of those Observations, when they shall come to our Hands, we may (if need be) make them publik: Which Observations, as they are in themselves very remarkable, and argue the Excellency of the Glasses by which they were discovered; So are we, in part, beholding to Monsieur Cassini for them, who giving notice before-hand of such Appearances to be expected, gave occasion to those Curious Observers to look for them.

Besides that Transient Shadow last mentioned, there hath been observed, by Mr. Hook first (as is mentioned in of these Transact.) and since by M. Cassini, a permanent Spot in the Disque of Jupiter; by the help whereof; they have been able to observe, not onely that Jupiter turns about upon his own Axis, but also the Time of such conversion; which he Rh