PROCEEDINGS OF SOCIETIES. 



Dublin Microscopical Club. 

 20th January, 1876. 



On the structure and presumed transformation of Irish, Litne- 

 stone. — Professor Hull, F.E.S., exhibited a thin slice of the lime- 

 stone of Haulbowline Island, Co. Cork, in confirmation of his 

 view that the rock has undergone a complete transformation 

 since its original deposition : assuming that the Carboniferous 

 Limestone of Ireland, where unaltered, always showed either to 

 the eye or under the microscope, organic structure, it was argued 

 that when found with the crystalline structure only, the original 

 rock had been subsequently replaced. In the case of the Haul- 

 bowline limestone and of the red marble from the adjoining 

 quarries of Little Island, it was considered that a nearly com- 

 plete transformation had taken place, by which the planes of 

 bedding were nearly obliterated and numerous veins of calc-spar 

 had been introduced. Professor Hull believed this process to 

 have taken place after those terrestrial disturbances by which the 

 Carboniferous Rocks of the South of Ireland were forced into 

 numerous flexures, and he gave an account of the manner in 

 which he considered that, through the agency of water charged 

 with carbonic acid gas, the original limestone had been dissolved, 

 and from time to time redeposited in the crystalline form. The 

 thin slices showed clearly the planes of cleavage of the rhombo- 

 hedron traversing the rock in various directions, sometimes in 

 slight] y curved lines, and along with this was a total absence of 

 organic structure. 



Exhibition, neio to Ireland, of the new parasitic Ithodosperm — 

 Ghoreocolax Polysiphonice, Reinsch. — Dr. McNab showed for the 

 first time in Ireland the newly discovered parasitic rhodosperm, 

 Ghoreocolax Polysiphonice, E-einsch, found by him on some ex- 

 amples of that alga taken at Salthill, Co. Dublin. These form 

 little cellular hemispherical prominences on the host, when older, 

 lobed ; in at least one instance, the "rootlike" immersed portion 

 of the parasite could be traced down into the substance of the 

 host Polysiphonia. These only lately discovered coloured para- 

 sites formed a subject of great interest, and much credit was due 

 to Professor Eeinsch in having directed attention to so many 



