4 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



in nature, and false dips are given, by which the very lowest beds are 

 made continuous with the highest parts of the series. It pains one 

 therefore to find such statements as the following: — "Fortunately 

 a rigid topographical detail is but of little moment ; " " and there is 

 the less reason therefore to dwell on those minutiae, though they 

 have been examined in the most scrupulous manner ;" "commencing 

 from the lowermost beds, it must be remarked, that it is impossible 

 to trace their common boundary with the red sandstone*." And 

 there are many other passages where, by a similar bold assertion or 

 by a certain vagueness and ambiguity, the author leads his readers 

 to take for granted what he affirms, and to give him credit for having 

 observed a great deal which he has not thought it necessary to 

 narrate. 



These remarks are made with much diffidence and reluctance. It 

 is a delicate task to criticise the labours of one of the earliest culti- 

 vators of geological science, especially one of his works which has ever 

 ranked among the standard treatises on British geology. And when 

 I reflect that his account of this limited area is one of the fullest 

 and most elaborate parts of his " description," embracing about 

 twenty-five pages of letter-press, I am sensible that my remarks tend 

 to throw a shade of discredit over other portions of his work on the 

 Western Islands. But it was impossible to pass over the subject in 

 silence. 



The lowest bed of the lias (PI. I. fig. 2) is a sandy conglomerate, 

 averaging 2 or 3 feet in thickness, and traceable from near Lussay at 

 intervals along the boundary-line to Heast. It is formed of well- 

 rounded pebbles of red sandstone and white quartz — the waste of 

 the surrounding knolls that formed reefs and skerries when the Scot- 

 tish lias began to be thrown down. To this succeed, at Lussay, 

 beds of white and greenish chloritic sandstone, varying from 3 or 4 

 to fully 15 feet in depth. Next follows a seam of dark-blue com- 

 pact limestone about a foot thick, surmounted by a stratum, irre- 

 gularly 2 feet deep, of massive Isastrcece enveloped in a dark sandy 

 clay. This remarkable bed escaped the notice of Dr. Macculloch : 

 it was first observed by Sir Roderick Murchison ; and afterwards 

 examined and describedf by one who has scarcely left a district of 

 his country unvisited, or unrecorded by his classic pen — the late 

 lamented Hugh Miller. 



I have not succeeded in detecting the coral-bed in the interior of 

 the island ; it probably thins out at no great distance from the shore. 



Above the corals there are 7 or 8 feet of a calcareous grit, which 

 shades off into a series of dark blue limestones with occasional courses 

 of shale. The calcareous beds are not peculiarly fossiliferous, show- 

 ing however on the weathered surface mouldering casts of Ammonites 

 and Gryphcece, and on a fresh fracture the minute joints of Penta- 



* Description &c. vol. i. pp. 316, 317. 



t In a paper read before the Royal Physical Society of Edinburgh, 21st April, 

 1852. This coral was mentioned at the Cheltenham Meeting of the British 

 Association by the Rev. P. B. Brodie, to whom I sent a specimen. See also 

 Edinb. New Phil. Journ. April 1857, p. 263. 



