Mr. Fekguson on Geology of Buchan. 33 



phora pustulata and tlie Lccanora tartarea. Beta-orcine was also shown. 

 It is tbe principle analogous to orcine, and is obtained either by boiling 

 usnic acid with excess of alkali, or by subjecting it to destructive distilla- 

 tion. Likewise erythro-mannite, a sweet crystallizable body obtained 

 from the Eoccella montagyiei ; and quinto-nitrated erythro-mannite, the 

 detonating compound analogous to quinto-nitrated mannite. 



The Society afterwards resolved itself into a conversational meeting. 



Wih April, 1849. — Tlie President in the Chair. 



Mr. Egbert Sinclair and Mr. Howard Bowser, were elected members. 

 The following paper was read : — 



VI. — On the Geological features of part of the district of Buchan, in 

 Aberdeenshire, including notices of the occurrence of Chalk- Flints, and 

 Greensand. By William Ferguson, Esq. 



The general features of the district to which I purpose calling your 

 attention, are those usually exhibited where the primary or crystalline 

 rocks predominate : at the same time one or two interesting anomalies, 

 are presented, or at least what presently appear anomalies, though a 

 more minute investigation, and more extended observation of facts, may 

 clear them up. 



I shall attempt to sketch, generally, the features presented by the 

 district, and then more minutely describe the peculiarities I refer to ; 

 the principal of these being the occurrence of a deposition of chalk-flints, 

 and greensand. 



Commencing our survey at the mouth of the Ythan, and proceeding 

 northward, the coast line is very bold and precipitous, broken, however, 

 here and there with cieeks and bays. From the Ythan, the parish of 

 Slains extends six miles along the coast. The average height of the 

 rocks is from 170 to 200 feet, and they consist of gneiss and mica slate, 

 with numerous veins of quartz ; and at one part of the coast they are 

 overlaid by limestone. I had occasion to traverse on foot several miles 

 of this coast last summer. I approached it at the village of Collieston, 

 where, in building the cottages of which it is composed, advantage has 

 been taken of a ravine, which ufl'ords a comparatively easy access to the 

 water. Part of the village is built on the water edge, and part on the 

 cliff, 200 feet above. A very deep deposit of clay covers ' the cliffs, 

 curling over them as it were, and presenting a steep slope covered with 

 grass, leadin;; to them. In some places the clay reaches to nearly the 

 water edge, but in no instance, that I saw, touches it, an outlier of rock 

 shielding it from the action of the water. In one place the overflow of 



Vol. III.— No. 1. 3 



