1865.] HERSCHEL EHOMBOIDAL SPECIMENS OF IRONSTONE. 421 



Of the forces which have impelled the fluids through the pores of 

 the spar I can give no satisfactory explanation. It is certain that 

 both in the SUver Band and Dufton Fell caverns, the moisture oozing 

 out of their sides contained iron, at least in solution, for the arra- 

 gonite was discoloured wherever the water had slowly streamed over 

 it. It is only when their elements combine chemically that bodies 

 crystallize. So far, however, as arragonite is concerned, a separation 

 of the unsuitable elements must be effected before the fluids are drawn 

 or forced into the pores of the spar. It has been suggested to me by 

 a friend that this separation may be efifected by osmosis ; and it is pos- 

 sible that the fluids may circulate in the pores by capOlary attraction, 

 and that, when these reach the surface or points of the stems, and the 

 superfluous portion of carbonic acid evaporates, the crystallization of 

 the lime is then effected in definite proportions with the remainder. 



Such are the conditions connected with the growth of arragonite. 

 Most of the minerals found in the lead veins traversing Mountain- 

 limestone in the north appear to be deposited from fluids filling up 

 and slowly circulating through the openings or interstices in the 

 veins. Arragonite growing in an atmosphere may be considered a 

 type of vegetation, the forms of which it more especially mimics. 



3. Notes accompanying some Rhomboidal Specimens of Iron-Sand- 

 STONE, ^"c. presented to the Society. By Sir J. F. W. Herschel, 

 Bart., K.C.H., F.B.S., F.G.S., &c. With a Note by Captain T. 

 LoNGWORTH Dames. 



[Communicated by Sir C. Lyell, Bart., F.E.S., F.a.S.] 

 (Abstract.) 

 Most of these specimens came from a quarry at Clanmullen, near 

 Edenderry, King's County, and the remainder from the CoUingwood 

 Quarry, in the Weald of Kent. The Irish specimens are siliceous, 

 containing some oxide of iron and a little manganese, and are homo- 

 geneous throughout. They all agree in the sharpness of definition 

 and the exact parallelism and evenness of the flat surfaces ; but, like 

 those from the Weald, they are not constant in form or size, and 

 sometimes are very irregular in angle and in the parallelism of oppo- 

 site sides. The Wealden specimens, however, are all closed boxes, 

 each containing a rhomboid of hardened sandstone, the outer case 

 being highly ferruginous — in fact, the " Ironstone of the Weald." 

 Sir John Herschel endeavoured to account for the formation of the 

 boxes, and Captain Dames added a Note stating the circumstances 

 under which the Irish specimens occiu\ 



May 10, 1865. 

 Absalom Bennett, Esq., Marazion, Cornwall ; Joseph Brown, Esq., 

 Q.C., of the Middle Temple, 54 Avenue Road, Regent's Park, N.W. ; 

 The Rev. John Magens MeUo, M.A., Incumbent of St. Thomas's, 

 Brampton, Chesterfield ; and George Noakes, Esq., 3 Grosvenor 

 Villas, St. Bartholomew Row, Holloway, were elected Fellows. 



The following communications were read : — 



