RECENT GEOLOGICAL WORK AT THE LIZARD. 
117 
group already recognised, there was a third, or granulitic group, 
occurring between the Balk Quarry and Kennack Beach. 
9. These groups formed but one series, enumerated in ascending 
order. 1. Characterised by dull green schists, and by brown 
mica schists. 2. By black lustrous hornblende-schists, sometimes 
rather massive, sometimes beautifully banded with felspar or 
epidote. 3. By pinkish-grey quartz-felspar rock, closely inter- 
banded with dark hornblendic or micaceous layers. 
10. The schists were all Archaean. 
These conclusions Professor Bonney still held, subject to some 
slight modifications. In a letter which appeared in the Geological 
Magazine for December, 1887, he wrote: "I admit, however, 
that when I wrote my two papers I sometimes failed to distinguish 
between the structure significant of original constitution, and 
those due to subsequent mechanical action, for our knowledge 
of the latter is of very recent date ; but to what extent I will not 
venture to say, until I can again examine the whole district." 
Mr. J. H. Collins, in a paper on "The Serpentine and Associated 
Eocks of Porthalla Cove," published in the Quarterly Journal in 
1884, challenged Professor Bonney's views as to the origin and 
order of the rocks in that district. He writes : "While I do not 
deny that in some instances even in the Lizard district masses of 
highly-basic and distinctly-intrusive igneous rocks may have been 
altered into serpentine, yet in this case (Porthalla) the evidence is 
altogether the other way. Careful examination of the cliff sections 
affords evidence of stratification in the serpentine, both on the 
large and on the small scale (i.e. of the serpentinous change 
of stratified materials in situ). This conclusion is supported 
by the chemical analysis of hand specimens, as well as by their 
macroscopical and microscopical appearance. Finally, I cannot 
see any sufficient reason for referring these metamorphosed rocks 
to any Archaean series. ... I believe, in short, that the Lizard 
rocks may be Archaean, but that those of Porthalla are of much 
later origin, and most probably Lower Silurian." 
In reply to a letter from Mr. Alexander Somervail, of Torquay, 
supporting Professor Bonney's views, Mr. Collins wrote, in the 
Geological Magazine for July, 1885, "What I believe is, not that 
the 'slate' has been altered into serpentine, but that of an 
originally differing series of conformable bedded rocks some 
beds have been converted into that peculiar variety of hornblendic 
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