1823.] Col, Beaufoy^s Astronomical Observations. 199 



Article VII. 



Astronomical Observations f 1823. 

 By Col. Beaufoy, FRS. 



Bushel/ Heath, near Stanmore. 

 Latitude 51° 37' 44'3" North. Longitude West in time V 20'93". 



Aug. 6. Immersion of Jupiter's second < 1 5h 25' 31" Mean Time at Bushey. ' 

 sateUite J 15 26 b2 Mean Time at Greenwiclu 



Article VIII, 



Essays on the Construction of Sea Harbours, 

 By Mr. J. B. Longmire. 



(Concluded from p. 15.) 

 SIR, July 18, 1823. 



With regard to the right direction of the piers, so as to throw 

 the most of the surf to the shore, and as httle as possible towards 

 the mouth of a harbour; it is necessary first to ascertain the 

 direction of all gales, that raise heavy surves at that place. Land 

 gales at a harbour are harmless in this respect; and so in 

 general are all gales making less angles with the main shore 

 than 15°; so that all dangerous gales as to surf, lie in about 

 150° directly in front of the harbour. But some situations have 

 not more than 130° of strong surf, and the most leeward of such 

 surf, at the mouth of a harbour facing the calmest quarter, makes 

 an angle of 45° with the main shore. 



Certain considerations have almost 

 universally prevailed in forming har- 

 bours. A sheltered situation has been 

 selected, either in a creek, or near a 

 part of the main shore that projects 

 into the sea. The mouth faces that 

 side which is the least disturbed by 

 sea gales. The same plan, or at least the same principle, has 

 been adopted as to the piers ; if in a creek, the main pier, a, 

 fig. 4, begins at the abrupt side, and extends either in a 

 line parallel to the main shore, or inclines a little inwards. This 

 pier has the best direction for quieting the interior water, and 

 preventing the surf from disturbing the entrance, both being 

 taken equally into consideration. But one pier alone placed in 



