Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/520

 silicification not so great as might at first sight appear ; for in Antigua and elsewhere vegetable forms had been converted into flint as completely and distinctly.

Mr. Woodward cited the hot springs in the Island of St. Michael as converting portions of vegetables still growing into flint. He had heard of the ends of piles being converted into flint in the course of thirty years, but had not yet seen them.

Mr. Jenkins inquired whether the Osmundaceae from different formations offered any evidence of the climate under which they lived. He thought that where vegetable structures were perfectly preserved in flint, the process of silicification had gone on but slowly ; but this fell more within the province of the chemist than the geologist. Mr. Hulke suggested the possibility of the fern having contained a certain amount of silica while still living.

Prof. Morris referred the fossil to the Thanet Sands. He thought that the silica in fossilized coniferous and endogenous wood varied in character, and this might throw some light on the process of conversion. He considered that objects containing phosphate of lime, and those containing carbonate of lime, were subject to different processes of silicification.

Mr. Whitaker was strongly of opinion that the fossil had been derived from quite the upper part of the Thanet Sands.

Prof. Duncan called attention to the process of silicifiation as exhibited by the Antiguan corals, in which one highly insoluble mineral had been replaced by another almost as insoluble. Mr. Carruthers, in reply, did not think that any thing could be predicated as to climate from extinct species ; if this were attempted, a similar error to that with regard to the climate under which the fossil Elephants were supposed to have lived, might be repeated. Existing Osmundaceae contained no silica in their structure. The peculiarity of the fossil under consideration was the preservation of the contents of the cells, even to the starch, which is so readily decomposed. The difficulty of accounting for the replacement of soft vegetable matter by hard mineral silica, seemed to him great.

2. The Oolites of Northamptonshire. By Samuel Sharp, Esq., F.S.A., F.G.S.

Introduction.

It is not without misgiving that I venture to offer to the notice of the Geological Society the following Memoir — justified in its production only by the fact that, during a residence of some years in Northamptonshire, I have been enabled, in the intervals of much other occupation, to acquire some familiarity with the geology of my own neighbourhood, and to make a collection of local fossils, which, in deference to " the inexorable logic of facts," I cannot but anticipate will prove of greater importance, as illustrative of the geology of the district, than any paper of which I may be the author.