424 LONGA. GENERAL DESCRIPTION. 



LONGA.* 



THIS small island lies to the north-east of Scalpa, and 

 though, like many others noticed in this work, void of 

 interest in itself, becomes important from its connexion 

 with the surrounding tracts, and from affording a visible 

 point in the sea which serves for the mutual approximation 

 of the rocks that compose them. 



It appears to be about a mile and a half in circum- 

 ference, forming an uneven table land which is abrupt 

 all round and about 200 feet in height; being the habi- 

 tation of sheep and the resort of gulls and cormorants. 

 Its structure and composition are so simple that it may be 

 described in a few words. 



It is entirely composed of red sandstone consisting of 

 beds lying in a north-east position and dipping to the 

 north-west ; in both of which respects they are con- 

 formable to the rocks on the opposite shore of Sky and 

 in the island of Pabba. Occasionally the beds are bent, 

 and separated by wide fissures ; while the sea, acting 

 on the softer strata, has excavated many of them into 

 caves similar to those by which quarries are sometimes 

 wrought, and much resembling the entrances of the well 

 known lime quarries of Arran. The strata are also tra- 

 versed by trap veins, attended, as 4 far as I could perceive, 

 with no unusual appearances. 



Comparing the dip and direction of the strata of Longa 

 and those of Pabba, it might be supposed that the former 

 were superior in position to the latter, as well as to those 

 of the corresponding shore of Sky ; an improbable circum- 

 stance, since this limestone, already ascertained to lie 

 above the red sandstone of the Kyles district, cannot be 



* Sec the M?ip of Sky, for the elucidation of which this ibland has also, 

 like Soa, IK en removed from its appropriate place. 



