182 MINERALOGY OF THE LIZARD DISTRICT. 



3. Had they been the product of contact metamorphism, such 

 a grand series of crystalline rocks would only be found in close 

 proximity to necks and dykes, and even then olivine would be 

 wanting. 



In conclusion, I think I have proved that the rocks lying be- 

 tween the Black Head and Porthallow, the N.E. of the Lizard 

 district, are composed entirely of volcanic or igneous minerals, and 

 are now passing through the phases that such matter is found to 

 undergo in other regions. 



The " Problem of the Lizard Rocks," which has proved a 

 complicated one to many a savant, is, in my opinion, now solved, 

 and I feel sure that all further investigation by those who are really 

 interested, will confirm it. 



The following is an explanatory list of the slides presented to 

 the Museum, where they can be studied. 



Slide 1. — From South of Coverack. — (plate A fig. 1) — Enstatite, olivine, and 

 serpentine after olivine, and enstatite showing symptoms of 

 change. 



Slide 2. — From South of Coverack, consisting principally of olivine and 

 enstatite in their characteristic changes into serpentine. 



Slide 3. — From a gabbro, N. of Coverack — (plate A fig. 3) — Consisting of 

 augite, felspar and olivine, very fresh, without any perceptible 

 change in the mineral. This was the slide seen by Prof. Judd. 



Slide 4. — From N. of Coverack — (plate A fig. 4) — Olivine and felspar in 

 contact, and their change into hornblende advancing. 



Slide 4a. — From N. of Coverack — (plate B fig. 5) — A kernel of olivine 

 surrounded by hornblende, in contact with felspar, illustrating 

 the general change of the mineral in this region. 



Slide 5. — From N. Coverack. — (plate B fig. 6) — Shows the mutual relation 

 that exists between olivine and augite ; here no dissolution 

 appears, but where olivine and felspar have been in contact, 

 antagonism has been at work, and out of their wreckage new- 

 formed hornblende has appeared. 



Slide 6. — From Near Dean Point. — (plate B fig. 7) — A small piece of olivine, 

 as if in a vase of augite. A unique specimen, in the problem 

 of the passage of the various minerals into hornblende. 



Slide 7. — From Coverack. — Contains both old and new minerals. In the 

 old rock is found olivine, enstatite, and anorthite ; the latter 

 mineral is much changed, but sufficient lines of the original 



