480 PHILOSOPHICAL TRANSACTIONS, [aNNO 1681. 



vessel will be 2155-1- ounces, or 179 pounds and 7f ounces : so that by drawing 

 out that air, the vessel is 25 pounds and 7f ounces lighter than air ; so that 

 that air being evacuated, the vessel will not only ascend into the air, but also 

 carry with it on high a weight of 25 pounds and 7^ ounces. And thus by in- 

 creasing the bulk of the vessel, without increasing the thickness of the brass 

 plates, he supposes a kind of ship or other vessel may be made to rise up in the 

 air, and carry men up with it.* 



^71 Occultation of Jupiter by the Moon, June 6, Neiv Style, in the Morning, 

 Observed at Dantzic, by M. Hevelius, Translated from the Latin. Philos. 

 Collect. N° 1, p. 29. 



Although I have watched and observed the heavens for 50 years past, yet I 

 have only once in all that time seen Jupiter covered by the moon, which was in 

 the year 1646, Dec. 24, New Style, in the evening, when the sun was under 

 the horizon. So that I very much congratulate myself that I could make this 

 observation, not only with a very clear sky, but also according to my wish, in 

 the presence of my very welcome guest, the learned and celebrated Mr. 

 Edmund Halley.-j- 



Jupiter entered behind the moon at mount Audus ; and, as far as could be 

 expected from its exit, it passed through the Loca Paludosa of the island Car- 

 cinna, over mount Actua, through the island Besbica, through Byzanticum, 

 the island ApoUonia, and the upper part of Palus Maeotis ; so that he went a 

 little above the moon's centre; the moon having then some south latitude. 

 Then, which is very uncommon, we measured, I think very accurately, the ap- 

 parent diameter of Jupiter in this observation. I remember that formerly I have 

 several times measured that diameter by means of the lunar spots, and found 



* Father Lana next proceeds to explain and direct the methods of making the machine, of ex- 

 hausting it, and obviating some difficulties which he conceives may occur in that process, and in the 

 managing of it, when floating in tlie air, by endeavouring to give it any particular direction ; also to 

 cause it to rise higher, he directs to throw out ballast or weights, and in order to descend lower when 

 needful, open a stop-cock to let out more air, &c. much in the manner as practised by the aeronauts 

 of the present day. And although the business could not be accomplished in his way of managing it, 

 nor the sides of so large and thin a vessel be sustained from crushing by the pressure of the atmos- 

 phere, for want of the knowledge of another kind of air, as elastic as the atmosphere, and yet many 

 times lighter, to fill the globe with, thereby rendering it at once both light and strong : yet the 

 paper is very ingenious and curious, and probably may have furnished hints to the more modem philo- 

 sophers to bring to perfection, in our time, what Father Lana and others had only surmised and con- 

 ceived as possible. 



t Who had been sent to him to settle a dispute with Mr. Hook, concerning the difference in 

 observing, between plain and telescopic sights. 



