Environs of Nice, and the Coast thence to VintimigUa. 185 



equivalent of coral-rag. To assign equivalents for beds which we have never 

 seen, and which Ave know only by description and very imperfectly, is a 

 practice highly reprehensible, and tends to nothing but confusion. 



The very great importance frequently attached to hand-specimens is in- 

 jurious to the progress of geology. It leads those who are unaccustomed to 

 examine the development of the same formation in different and distant 

 countries, to believe, tliat a similarity of external mineralogical character is 

 necessary to establish its geological identity. That this is not true in regard 

 to the dark clay of London, and the light coarse limestone of the Paris basin, 

 is well known ; yet many geologists are not so completely sensible of the little 

 value of mineralogical character under such circumstances, as to find, without 

 surprise, that beds of gypsum and dolomite are members of the oolite forma- 

 tions. They, however, have every appearance of being so in the neighbour- 

 hood of Nice ; and the anomalies which the green-sand formation present to 

 us in the same neighbourhood, afford another practical lesson, that a minute 

 attention to mineralogical distinctions, and an accurate examination of hand- 

 specimens are, on many occasions, even worse than useless, and tend rather 

 to mislead the geologist than to instruct him. 



Additional Note, August 5, 1829. — Since the above was written, much 

 additional information, derived more particularly from my friend M. Elie de 

 Beaumont, would seem to render it probable that the Nice light-coloured 

 limestones and dolomite, either constitute the lower part of the great green- 

 sand formation, or the upper part of the oolite system. Prom an extensive 

 series of observations, M. Elie de Beaumont is led to consider the nummulitic 

 beds of the Alps as intimately connected with the light-coloured limestones of 

 Nice, of Provence, of La Fontaine de Vaucluse, of Mont Ventoux, of the 

 departments of the Drome, the Isere, &c. ; the nummulite-rocks at the same 

 time being connected with the well characterized deposits of Brian^onnet 

 (Basses Alpes), of Villard de Lans (Isere), of the mountains of tiie Grande 

 Chartreuse, of Mont du Chat, of the high longitudinal valleys of the Jura, of 

 the Perte du Rhone, of Thonne, and of La Montagne des Pis. Whatever 

 may be the age eventually given to the Nice limestones, it would appear from 

 the observations above noticed, and others, which it would be out of place 

 here to detail, that the nummulite-beds of the same neighbourhood belong to 

 the green-sand formation, and not, as might be supposed, from a partial exa- 

 mination of the Alpine nummulite-rocks, to any tertiary deposit. 



VOL. III. — SECOND SERIES. 2 B 



