Geological Society. 543 



Hare, as in other cases, the tables are supplemented by the corre- 

 sponding curves or graphs. This graphical representation is 

 indeed an extremely important feature throughout. Each Table 

 is accompanied by an exposition of the theory sufficient to refresh 

 the memory of the worker in applied mathematics who wishes to 

 make use of it. In most cases the values are given to four or five 

 significant figures. The names of the authors are a guarantee of 

 the care that must have been taken in preparing this most timely 

 publication. 



T 



LVI. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xix. p. 918.] 



January 26th, 1910.— Prof. W. J. Sollas, LL.D., Sc.D., F.R.S., 

 President, in the Chair. 



HE following communications were read : — 



1. 'On a Skull of Megalosaurus from the Great Oolite of 

 Minchinhampton.' By Arthur Smith Woodward, LL.D., F.R.S., 

 F.L.S., Sec.G.S. 



2. ' Problems of Ore-Deposition in the Lead and Zinc Veins of 

 Great Britain.' By Alexander Moncrieff Finlayson, M.Sc, F.G.S. 



Chemical analyses show traces of lead and zinc in several of the 

 rock-formations of Britain, but the ores of the veins are concluded 

 to be derived, not from the country-rock, but from deeper sources, 

 probably in the first place by magmatic segregation. They were 

 transported in the deeper zones by 'juvenile' waters, in which 

 fluorine was an important constituent, while in the upper zones, 

 especially in limestone districts, underground waters of meteoric 

 origin have played a large part. The vein-solutions carried (J ) 

 alkaline sulphides, which held the sulphides of the metals in 

 solution, and (2) alkaline and earthy carbonates. The presence 

 of the latter is indicated by the alteration of the wall-rock, which 

 shows a concentration of potash, lime, and carbon dioxide, and a 

 leeching of soda, magnesia, oxides of iron, and silica. In lime- 

 stones, however, the chief effects of solution on wall-rock were 

 concentration of silica and magnesia. 



The filling of fissures rather than direct replacement of rocks by 

 ores, has been the chief process, but the calcium of fluorspar has 

 been very largely derived from the country-rock. Further, much 

 local metasomatism is seen, such as replacement of limestone by 

 fluorspar, galena, blende, and quartz ; and replacement of fluorspar 

 by galena. 



The order of deposition, determined by microscopic examination 

 of polished specimens of ores, has been : chalcopyrite, fluorspar, 



