132 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 1 894,. 



suggested that the banding of the hornblende-schists was produced 

 by the action of water, such as circulates about the roots of 

 volcanoes, leaching out unstable minerals, like pyroxene, from the 

 spaces between tbe planes of lamination, and the formation of com- 

 paratively stable minerals, such as hornblende, along those planes. 

 Tbe Lizard rocks he regarded as containing good examples of the 

 formation of hornblende in the wet way, that mineral having been 

 deposited in cracks so as to join together the ends of hornblende 

 crystals. The Author considered the ' granulitic ' group as in part the 

 result of converted ash-beds, whilst other portions are composed of 

 intrusive diorites of later date, the quasi-bedded appearance of both 

 being due to the injection of granite. In some places the intrusive 

 character of the granitic veins is undoubted. On the whole, it 

 would seem that this paper was written at a time when the Author 

 wished to protest against every case of foliation being quoted as 

 an instance of dynamic deformation, though on several points he 

 was content to suspend his judgment for the present. 



The next paper on the Lizard Rocks was a joint contribution from 

 Prof. Bonney and General M c Mahon, being the results of a visit in 

 August 1890. The Authors maintained that the peridotite, from 

 which the serpentine is derived, was introduced into the hornblende- 

 schist and banded granulitic rocks, after these had assumed their 

 present condition. They assert that there are no signs of any 

 marked pressure-metamorphism in this rock either prior or posterior 

 to serpentinization. The streaky or banded structure they have failed 

 to connect with any foliation or possible pressure-structure in the 

 schists, and they are disposed to regard it as resulting from move- 

 ments while the mass was still in a molten or partially molten 

 condition. The occasionally banded structure in the gabbro they 

 also regard as resulting from a kind of fluxional structure. They 

 now held that the ' granulitic ' group consists of at least two distinct 

 rocks — one acid, the other basic, — of which the former was intrusive 

 in the latter, and that, certain fluxional movements ensuing, the 

 uniform and stratified aspect of the two varieties was thus produced ; 

 this movement being followed by crystallization, or completion of 

 crystallization, in the constituents. The hornblende-schists they 

 were content to leave a somewhat open question ; and, lastly, they 

 held that earth-movements have produced marked effects only at the 

 extreme north and the extreme south of this district, those on the 

 northmodifying the rocks for a very limited distance. 



The latest communication to the Society on the subject of the 



