TKANSACTIONS OF SECTION C. 543 



That given above does not agree with any known types of silicate. Supposing it 

 to be a mixture of peroxide and silicate, we should get the formula — 



[H 6 M'"A + (M" 3 M'",Si,A 8 ) + 4H.P], 



a mixture with a meta-silicate, on the type, H 12 Si,;0, 8 , corresponding with the 

 talc and chlorite series. Or, supposing it to he a mixture of an aluminate, or 

 ferrate, with a silicate, we get a formula not unlike that proposed for Bipidolite, 

 viz. — 



[M" S MA + M'^IIgSiAg + 4H 2 0], 



a part of the water being basic. Either of these formulas seems probable. 



Its low specific gravity and its resistance to the blowpipe are remarkable, con- 

 sidering the large amount of iron. 



The author proposes to name this mineral Hullite, after Professor Hull, who 

 has done much valuable work in elucidating the microscopic mineralogy of the 

 basalts of Ireland. 



Part II. — Microscojric structure of the Basalt. — Professor Hull describes the 

 microscopic appearance of the mineral, and of the rock in which it occurs. The 

 basalt contains short prisms of augite imbedded in a paste of plagioclase felspar, a 

 great deal of olivine, and the mineral described above in abundance. Under the 

 microscope, the latter is of a dark amber brown colour, nearly opaque. It per- 

 meates the whole rock, filling the interstices, and enclosing the other minerals. It 

 does not polarize, and is, therefore, not crystalline, but assumes very much the 

 character of amorphous chlorite, being apparently, like it also, a secondary 

 mineral formed after the consolidation of the rock. 



The rock contains an abundance of olivine, not seen in such quantity in any 

 other basalt of Antrim, and hardly ever so fresh and unaltered. In most cases 

 the outer form only is preserved ; but here it is as fresh as in the lavas of 

 Vesuvius. From this it might be inferred that the rock was comparatively recent, 

 did we not know it to be older than the Glacial and Pliocene periods. 



3. The Progress of the Geological Survey of Ireland. 

 By Professor Edward Hull, M.A., F.E.8., Director. 



(With the Sanction of the Director-General.) 



The author gave a short account of the progress of the Survey from its com- 

 mencement in 1832, under the late General Portlock, R.E., down to the present 

 day, stating that the whole country south of a line drawn roughly from Lame, 

 on the coast of Antrim, to Sligo, had been surveyed, while 160 sheets of the. 

 geological map on a scale of 1-inch to the statute mile had been published. 



Along with these had also been issued 78 separate Explanatory Memoirs, 

 describing the structure and palaeontology of 12B sheets. It had also been found 

 necessary to revise the geology of the Leinster and Tipperary Coal-fields, the 

 Carboniferous trap-rocks of County Limerick, and the south-east portion of the 

 country, including part of Wicklow and Wexford. The coal-fields of the North of 

 Ireland had also been surveyed, and published on maps both on the " 6-inch " and 

 41 1 -inch " scales ; and it was also intended that the districts of County Antrim, 

 containing the pisolitic iron ores, should be illustrated by maps on both scales. 

 The tract still remaining to be examined included the greater portion of the 

 counties of Donegal, Tyrone, Fermanagh, Sligo, and Antrim. 



4. Report of the Committee on Erratic Blocks.— See Reports, p. 185. 



