382 Geological Society : — 



The resemblance between curves of I=/(T) and p— /(T) 

 is more obvious than the resemblance between curves of 

 I = </>(H) and p — (f)(F) } as Curie pointed out, and the fluid 

 unalogy must be followed with caution. For example,, 

 account must be taken of the i';ict that I is a vector quantity, 

 whilst p has not this character. The hypothesis of the 

 intrinsic field needs careful scrutiny, and I have more thm 

 once referred to this. But I think one of Curie's doubts 

 may be allayed if the interpretation of magnetic hysteresis 

 according to the fluid analogy is correct. In the sentence 

 following the one quoted by Miss Bruins, Curie writes: 

 u La cmirbe d' aimantation stable, par exemple, dont nous 

 avons parle plus haut, n'a pas d'analogie chez les fluids . .. ."' 

 Now in the paper referred to above (p. 342) I have shown 

 that the curve of stable magnetization, called there an 

 anhysteretic isothermal, naturally u finds its place according 

 to theory side by side with the two branches of the hysteretic 

 loop," and from this point of view is analogous to the sudden 

 passage of a saturated vapour to the liquid state. 



XXXVL Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY, 



[Continued from p. 152.] 



March 28th, 1917.— Dr. Alfred Harker, F.R.S., President, 

 in the Chair. 



/J\HE following communication was read : — 



' The Carboniferous Limestone Series on the South-Eastern 

 Margin of the South Wales Coalfield.' By Frank Dixey, M.Sc, 

 F.G.S., and Thomas Franklin Sibly, D.Se., F.G.S., University 

 College of South Wales & Monmouthshire, Cardiff. 



The outcrop dealt with extends from the valley of the Ewenny 

 river near Bridgend (Glamorgan) to that of the Ehbw river at 

 K-isca (Monmouth), a distance of about 19 miles from west- 

 south-west to east- north- east. It is traversed by the rivers Ely, 

 Taff, and Ehymney. 



Traced north-eastwards along this outcrop, the Carboniferous 

 Limestone Series suffers much attenuation and becomes mainly 

 dolomitic, as shown by the officers of H.M. Geological Survey 

 during the recent re-survey of the coalfield. 



The table on p. 383 summarizes the succession in the western part 

 of the district. 



The Lonsdaleia Subzone (D 2 ) has not been recognized, and, 

 L£ represented, it is probably incomplete. Contemporaneous 

 dolomitization is of comparatively small vertical extent. 



