[ " ] 



miles diftant from the land, and about fifty feet above the 

 water. In particular ftates of the atmofphere, and more efpecially 

 on the approach of fevere weather, the Welfh mountains are 

 diftindly vifible, particularly that ridge of hills which runs 

 S. W. to point Braich-y-pwll, and bounds Caernarvon bay in 

 that diredion. 



I SHALL proceed to the particulars of the plan of this Ob- 

 fervatory. 



Plate I. is the elevation of the Eaft front. 



Plate II. is the ground plan. E is the bafe of a folid 

 pillar of fixteen feet fquare, which is of the mofl fubftan- 

 tial mafonry, and is raifed from the folid rock to fuch height, 

 that the centre of the equatorial inftrument, which it is to fup- 

 port, may overlook every part of the building. This inftrument 

 demands the entire range of the horizon, fince, as it is now 

 conftrudled, it may be applied to the moft valuable purpofes in 

 Aftronomy. It was a long time deliberated whether it would 

 not be better to fubftitute for this inftrument a vertical and 

 azimuth circle of the fame diameter, which has undoubtedly 

 peculiar and unrivalled advantages; but many circumftances of 

 fingular convenience in the equatorial, as alfo fome peculiarities 

 in its application, at length determined the choice in its fa- 

 vour. 



This fubftantial pillar is furrounded by a circular wall at a 

 foot diftance, which is to fupport the turning dome, and the 

 floor of the room, which muft not be fuffered to touch the 



B 2 pillar 



