502 [Proc. B.N.F.C, 



secondary minerals found in the veins and vesicles of volcanic 

 lavas," such as the green earth series, zeolites, and siliceous 

 minerals, like chalcedony and opal. Most mineralogists at the 

 present day teach a theory tO' the effect that such minerals are 

 derived from percolating meteoric waters in the weathering and 

 rotting of the lava ; others teach that such minerals are derived 

 from the mother rock by a process of alteration which proceeds 

 apace during the last stages of the lava's cooling. By some 

 these minerals are regarded as original formations not formed 

 by fusion, but by crystalline forces of segregation and secretion, 

 which are at work during the final stages of the lava's con- 

 solidation. The lecturer then demonstrated his reasons for 

 accepting and developing tO' some extent the last of these in- 

 terpretations of observed facts, and proceeded to illustrate the 

 theory by applying it in detail to a number of secondary 

 deposits in various types of lavas, including basalts, andesites, 

 and rhyolites. The zeolites of Ballypalady, the chalcedony of 

 Carnmoney, and the opal of Sandy Braes were described in 

 particular. The lecture was concluded by a re-statement, with 

 slight modifications, of the " Law of Order in the Separation of 

 Secondary Minerals in Volcanic Lavas," as first expressed in a 

 paper read before the Club twelve months ago, and which 

 paper as a work of original research was printed as an appendix 

 to the proceedings of the Belfast Naturalists' Field Club for 

 1906. 



A very animated discussion followed the termination of 

 the lecture, the following members taking part : — Messrs. 

 Robert Welch, Andrew Duncan, Robert Bell, Robert May, W. 

 J. C. Tomlinson, S. Weir, and W. H. Gallway ; and, Mr. 

 Strachan having briefly replied, the meeting closed. 



" CLOUDS AND THEIR EVOLUTION." 



The third monthly meeting of the Winter Session was held 

 in the Museum, on Tuesday evening, 15th January, presided 

 over by Mr. W. J. Fennell, M.R.I. A. The usual science gossip 

 half-hour from 7-30 to 8 o'clock was well attended, and at 8 



