[ ,o ] 



four Englifh miles. The mercury in the barometer ftands there 



In. 



0,254 lower than at high water mark at the Liftey in fpring 

 tides, the thermometer being in Dubhn 62°, and at the Obfer- 

 vatory 59^*- It is founded on a folid rock of limeftone of 

 fome miles extent, which, near the Obfervatory, rifes to within 

 fix inches of the furface, and is fo hard as to require to be 

 blafted with gunpowder for the ordinary ufes of the farmer. 

 The foil around is compofed of loam and a fpecies of calcareous 

 fubftance, called in Ireland limeftone- gravel, which is very 

 abforbent. The horizon is remarkably extenfive, without 

 the fmalleft interruption on any fide, except that on the 

 South the Wicklow mountain?, diftant about fifteen Enghfli 

 miles, rife about a degree and a half. Their diftance feems to 

 remove all apprehenfion on account of their atlradion exerted 

 on the plumb-line ; and the gradual and equal acclivity of the 

 hill, on which the building is ereded, feems to fecure us from 

 any more near and dangerous local effedt in that refpe£l. 

 Confidered in another point of view, thefe mountains afford a 

 ftriking advantage, of which I have been frequently an eye wit- 

 nefs : When clouds are coming from the South, I have often feen 

 them arrefled by the mountains, leaving the fpace from thence 

 to my zenith ferene, whilfl to the Eafl and Weft, where no 

 fuch obftacles intervene, all has been obfcured with flying feud. 

 From E. to S. E. the fea is vifible, diftant about ten or twelve 

 miles, a circumftance which in fome particular cafes is not 

 without its ufe : But what I confider particularly happy, is the 

 opportunity afforded by the Light-houfe for obfervations on 

 terreftrial refradions both by night and day. This is near five 



miles 



* This the refult of one obfervation only. 



