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characters of the rocks of the locality, states that on the west shore 

 of the Bay of Durn serpentine alternates at least five times with an equal 

 number of beds of diorite. Two masses of serpentine occur to the west of Portsoy . 

 Portions of the larger of these form, when polished, a highly ornamental stone, 

 there being a mixture of blotches of a bright red colour throughout 

 a groundmass of green and white. The smaller, or more easterly 

 of the two masses, resembles an intrusive dyke, and terminates in the 

 sea. Typical gabbro occurs according to Dr. HEDDLE in a small 

 sea-stack, whereas the adjoining portion of the main mass shows a 

 transition from gabbro to serpentine. Dr. HEDDLE is of opinion that a 

 portion, if not the whole, of the serpentine has been formed by the alteration 

 of an augite-plagioclase rock. In view of the researches of TSCHERMAK, 

 BOXXEY and others, this seems highly improbable, and the present writer 

 possesses a slide of Portsoy serpentine, which not only shows the typical 

 " maschen-structur," but contains also original oliviue in the centres of 

 the meshes. In the face of this direct evidence of the occurrence of olivine, 

 it is to say the least, extremely doubtful whether any portion of the mass was 

 originally free from this mineral. 



Near Kirriemuir, in Forfarshire, occurs the remarkable dyke described by 

 SIR CHARLES LYELL (1) and Professor Jui)D. (2) It varies in width from 100 to 

 300 yards, and encloses masses of the rocks traversed by it. These rocks 

 belong to the Old Red Sandstone, and they are markedly affected by the dyke. 

 Professor JUDD says : " At its sides the rock is a mass of serpentine traversed 

 by numerous veins of chrysotile, and exhibiting no evidence of the minerals 

 from which the rock was originally formed. But towards the centre crystals 

 of " Schiller-spar " make their appearance, and the serpentine gradually 

 passes into a hard crystalline mass. Studied by the aid of the microscope this 

 central and least weathered part of the dyke is seen to be made of serpentine, 

 clearly pseudomorphous after olivine, and containing large crystals of a ferriferous 

 enstatite in a more or less advanced stage of alteration into bastite and 

 serpentine. In some portions of the mass of the dyke the ferriferous enstatite 

 prevails almost to the exclusion of the oliviue, and we have a rock strikingly 

 resembling the bronzite-rock of the Kupferberg, near Bayreuth, and of St. 

 Stephan in Upper Styria. Among the dykes which intersect the great 

 serpentine mass, I found one to consist of a coarse dolerite or augite-gabbro, 

 while another is a very beautiful example of a hypersthene (ferriferous 

 enstatite) dolerite." 



The occurrence of serpentine at the localities north of Aberdeen one in 

 the parish of Belhelvie, and the other on the shore close to the rock known 

 as the Black Dog has been noted by Dr. HEDDLE, ' 8) and the rocks have been 

 examined and described microscopically by Professor BOXNEY. (4) They consist 

 of serpentine derived from olivine, with the characteristic maschen-structure, 



(1) Edin. Jour., see vol. III. (1825) p. 112. 



(2) Q.J.G.S. Vol. XLL, 1885, p. 399. 



(3) Min. Mag. Vol. V., p. 1. 



(4) G.M. Decade III. Vol. II., 1885, page 439. 



