1869.] ORiLEROD— DAETMOOK GRANITE. ,. 277 



mile, mark the places to which the granite extended before it curved 

 down to the N. & S., as before mentioned. At Wattern tor (fig. 2), 



Fig. 2. — Wattern Tor, from the South, showing the decay along the 

 lines of North and South Joints. 



the chief mass is crossed by two north and south lines, along which 

 decay has acted, dividing the upper part into three masses, and 

 forming one of the most imposing tors on the moor. To the N.E. 

 of this tor there is a narrow ridge with low cliffs on both sides, 

 formed by parallel N. & S. lines of joint ; and at one place, in 

 consequence of decay along the E. & W. joint, the storms have 

 forced a passage, whence the tor has derived the name of Thirl- 

 stone. The E. & W. joints here are not perpendicular, but in- 

 cline towards the south ; at Honey-bag Tor, near Widdicombe, in 

 the moor, the inclination is towards the north. Near Manaton, on a 

 hillside, there is a solitary tor, " Bowerman's Nose," rising about 40 

 feet above a " clatter of rocks ; " its prismatic shape is probably 

 derived from the intersection of lines of joint. These tors have been 

 selected from many as a series of examples of the effect of lines of 

 joint, tracing it from the large massive cluster of rocks to the insu- 

 lated pillar. Belstone Tors in the hard granite, and Hound Tor in 

 the softer granite, are probably two of the best points for studying 

 the hues of joint, and the different varieties of bedding, and decay 

 along the lines of bedding, that occur in the east of Dartmoor. 



It has been before noticed that the granite at the northern part 

 of Dartmoor is more crystalline and compact than that to the south 

 of the North Teign ; in the last-named district is the broad belt 

 extending across Dartmoor mentioned in my paper on Rock Basins, 

 as containing those hollows (Q. J. G. S. xv. p. 16). In this south- 

 eastern division, in addition to the other sources of decay, is one 

 that arises from the spheroidal structure of the granite. Professor 

 "Warington Smyth, in his Presidential Address for 1868 (page 1.), 

 mentions that in Palestine blocks of granite decay from the centre 

 to the surface, giving rise to rounded hollows. That species of 



