432 MR. ]{. nOBSON ON THE IGNEOUS ROCKS 



24. On the Ignkous Hocks of the South of the Isle of Man. By 

 Bernard Horson, Esq., M.Sc, F.G.S., Assistant Lecturer in 

 Geology at the Owens College, Manchester. (Head April S, 

 1891.) 



[Flate XIV.] 



Contents. 



Page 



I. Previous Literature 432 



II. Main Features of the Geology of the District 432 



III. Types of Igneous Rocks met with 433 



IV. Detailed Description of the Geology of Scarlet Point, &c 43o 



V. Macroscopical and Microscopical Characters of the Rocks 43^ 



(rt) The Diabase Series. 



{b) The Micro-granite Dyke. 



{c) The Augite-porpliyrite Series. 



[d) The Melaphyre Dyke 



(e) The Picrite-porphyrite. 

 (/) The Olivine-dolerite Series. 



VI. Suppleineutaiy Obsei'vations 447 



VII. Summary 4-111 



I. Previous Literature. 



Though the igneous rocks of the Isle of Man have been cursorily 

 described by Berger*, Henslowt, and Macculloch J, the most satis- 

 factory account of them is contained in the work of the Hev. J. G. 

 Gumming § and in the paper by Mr. Home \\. The Eev. J. Clifton 

 AVard ^ has also given an interesting sketch of their geology. 



In the " Journal of the Liverpool Geological Association," vol. ix. 

 (1888-89) pp. 41-47, is a paper entitled '' Notes on some Manx 

 Lavas," by Isaac E. George, but it hardly contains much information. 



In the " Proceedings of the Liverpool Geological Society," vol. vi. 

 pt. i. (1888-9) pp. 123-131, is a paper on " An Examination of 

 some Volcanic Eocks of the Isle of Man," ** by Messrs. Dickson and 

 HoUand, containing analyses of 5 specimens, and a description by 

 Mr. Rutley of 10 specimens. 



IL Main Features of the Geology of the District. 



The greater part of the Isle of Man consists of slates, which are 

 usually held to be of Lower Silurian age, but in the south of the 

 island Carboniferous rocks occur. They occupy an area of about 7 

 square miles and overlie the slates unconformably, extending from 

 Cass-ny-Hawin on the east coast to near Athol Bridge over the 



* Trans. Geol. Soc. vol. ii. (1814) pp. 29-65. 

 t Ibid. vol. T. (1821) pp. 482-505 and pi. xxxv. 



j 'Western Islands of Scotland ' (1819), vol. ii. p. 571, and vol. iii. pi. sxvii. 

 I 'The Isle of Man' (with 8 pis. and 10 views), London (1848). 

 il Tmns. Edin. Geol. Soc. vol. ii. (1874) pp. 323-347. 

 ^ Geol. Mag. (1880) p. 5. 



** The writer was nnacquainted with this paper at the time of reading the 

 present one, so that all references to it have been added since. (June, 1891.) 



