502 ME. B. HOBSON ON THE BASALTS AND 



No. 911 (80 S.W.). Old quarry, 108 yards west of Barley House, 

 1^ mile S. 75° W. of Exeter. 



Nos. 912 & 912 A, B, (79 S.E.). Knowle Quarry, 3f miles S. 

 54° W. of Exeter, 1000 yards S. 75° E. of Darniford (house). 



No. 913 (79 S.E.). West Town Quarry, 1245 yards S. 87° W. of 

 St. Ida's Church, Ide, near Exeter. 



Nos. 914, 914 a (91 N.E.). Quarry behind Webberton Cottages, 

 467 yards N. 81° W. of Haldon House, near Dunchideock, S.W. 

 of Exeter. 



No. 915 (91 N.E.). Old quarry by roadside in * School Wood ' or 

 * Great Plantation,' 703 yards N. 66° W. of Haldon House. 



No. 916 (91 N.E.). Old quarry in Orchard Copse, 203 yards N. 

 62° W. of Holy Trinity Church, Dunchideock. 



Nos. 918 a, b, c, d (80 S.W.). Large quarry at Pocombe, close to 

 Crossmead, 1 J mile S. 60° W. of Exeter (cathedral). 



No. 919. Old quarry at West Clist(3§ miles N. 60° E. of Exeter), 

 opposite road turning off to Poltimore Park. 



Nos. 928 A & B (65 N.E.). ' Stone Quarry,' 545 yards N. 40° W. 

 of Crooke, and about 1 mile E.S.E. of North Tawton. 



Nos. 929 A, B, & c (67 S.W.). Large quarry, 220 yards N. 54° E. 

 of St. Luke's Chapel, Posbury, near Crediton. 



VII. Maceoscopical and Miceoscopical Chaeactees of the Eocks, 



Most of the * felspathic traps ' examined by me are altered 

 olivine-basalts, but the rock of Killerton (Nos. 900, 901, 902, 907) 

 is an altered andesite, and appears to differ from that at Columbjohn 

 Wood (No. 906) on the west and of Lower Budlake (No. 899 a, &c.) 

 on the east of it, although the Geological Survey map makes of them 

 all one continuous mass. 



(a) Altered OUvine-hasalts. 



These would be termed melaphyres according to the nomen- 

 clature of Prof. Eosenbusch,^ but since it is now pretty generally 

 admitted that the pre-Tertiary geological age of an igneous rock is 

 no sufScient reason for giving it a different name, and since the 

 use of the term ' melaphyre ' for an altered basalt ^ or olivine- 

 basalt^ only tends to conceal the relationship of basaltic rocks, 

 I prefer to call them basalts. 



Although on the whole there is a considerable resemblance be- 

 tween the macroscopical characters of the ' traps ' from the different 

 localities, yet the appearance of the rock varies so much even in 

 one and the same quarry, according to whether the freshest non- 

 vesicular or the most altered and amygdaloidal specimens are taken, 

 that no one description will apply to all cases. 



Tyjpe 1. Freshest non-vesicular rocks. Their colour varies from 



1 'Mikr. Physiogr. d. Massig. Gest.' 2nd ed. 1887, pp. 484, 506. 



2 F. H. Hatch, ' Introduction to the Study of Petrology,' 1891, p. 112. 



3 G-. A. J. Cole, 'Aids in Practical Geology,' 1891, p. 237. 





