TRANSACTIONS OF SECTION C. 585 



5. Newer tin lodes (Trevaimance, &c.), underlying northwards mostlj% 



6. Newest tin lodes (Trevaiinance, Wheal Owles, &c.) mostly underlying 



southwards. 



7. Older east and west copper lodes producing tin in depth (Dolcoath, &c.) 



8. Older caunter copper lodes. 



9. Older cross-courses. 



10. Newer east and west copper lodes (Wheal Peevor). 



11. Newer caunter copper lodes. 



12. Newest copper lodes (Wheal Peevor). 



13. Newer cross-courses and flucans. 



14. Newest flucans and slides, 



15. Alluvial faults. 



The author showed that the older fissures were occupied either with quartz, 

 together with tourmaline or stanniferous deposits (1, 3, 5), or else with granite and 

 felsitic matter (2, 4) ; that the fissures of intermediate age were occupied chiefly by 

 oxidised and sulphuretted copper ores near the surface, and hy tin ores in depth 

 (6, 7, 8, 10, 11, 12), or else by quartz, with small quantities of ores of nickel, cobalt, 

 ui-aniiun, &c. (9) ; while the newer fissures contained only quartz, oxide of iron, 

 galena, and blende (13, 14) ; while the newest of all contained little besides 

 clay (15). In all (except 2 and 4) there are evidences of the partial mechanical 

 infil ling of open fissures. 



In many cases the absolute amount of vertical displacement is small, in others 

 it cannot be exactly ascertained, the most marked eflfects in this respect being pro- 

 duced by the cross-courses and cross-flucans (9, 13, 14). These cross-courses, &c., 

 occur in great numbers between Hayle and Padstow, and owing to the fact that 

 the downthrows are nearly always on the east sides of the respective faults, the 

 total vertical displacement between these points cannot be less than 2000 feet, and 

 is probably much more. In this way, older and stiU older rocks appear at the 

 present surface as one proceeds westward. 



The author concluded by briefly calling attention to the physical efiects of these 

 fault systems as developed in coast-lines and valleys. 



6. On the Geology of the Balearic Islands. 

 By Dr. Phen^, F.S.A., F.G.8. 



In the two preceding years I have had the honour of drawing the attention of the 

 Section to the magnificent effects of lime deposits in the Grottos of Antiparos, and 

 to the almost mountainous dimension of the external deposits, called Pambuk 

 Kalesi, at Hierapolis, in Anatolia. 



There are some remarkable features in the geology of Minorca, in which 

 that science has a beneficially sanitary effect, though it is probable that experience 

 rather than scientific research produced in the first instance the effect, and then 

 influenced popular opinion. 



The island is geologically divided into two complete sections, which face each 

 other in a continuous and very slightly de-viating line from north-west to south- 

 east. The southern portion is an almost uniform rock of Miocene formation, wkich 

 occupies an area of more than half the island ; the more northern begins on the 

 east with a sea-coast of Devonian rocks running continuously to the north coast, 

 with a mean breadth of three miles, succeeded by Lower Triassic beds, which crop 

 up again further west, between which two portions is a broad Jurassic belt, curi- 

 ously meandered by Upper Trias, and succeeded again by a broad field of Devonian 

 formation. The large area of these various formations is -found to be unhealthy for 

 abode, though this may be entirely the result of latitude; but here at least they 

 seem to contract the moist vapours which often hover over all the islands, while 

 the rocky surface of the Miocene is much drier. All the large towns are erected 

 on the latter, as Mahon, Cuidadella, Alayor, St. Cristobal ; and Ferrerias is on the 

 border. 



In Majorca, to the north-west side of the island, the Jurassic formation rises 



