Geological Society. 



501 



be considered as a great development of the superior part of the 

 Upper Ludlow Rock. In M. Dumont's work, before mentioned, 

 lists are given of the fossils from each system ; and on examining 

 them, for the purpose of determining how far the comparison of the 

 Belgian and Silurian systems could be established by organic re- 

 mains, the author of this notice ascertained, that out of twenty-two 

 species, only four could be considered as peculiar to the Silurian 

 system ; and of these he believes two may be erroneous identifica- 

 tions ; that five species are common to the Belgian beds and the 

 mountain limestone, and thirteen to the Belgian and Devonian 

 systems. These lists, Mr. Lonsdale states, are small, but, he adds, 

 they bear internal evidence of having been carefully drawn up with- 

 out any preconceived theory ; and he conceives that they afford 

 sufficient proof that the beds from which they were obtained do 

 not belong to the Silurian system, but partake of the same inter- 

 mediate character as the Devonian limestones. The other case, 

 alluded to in the paper, refers to the older beds of the Bas Boulon- 

 nais. These strata were identified by M. de Verneuil in 1838, 

 with the Silurian series of England, particularly a bed of limestone 

 containing corals and other fossils with the Wenlock limestone ; 

 and M. Dumont, who examined the country with M. de Verneuil, 

 states in his report to the Bruxelles Academy, that his four systems 

 occur in the Boulonnais. The above bed of limestone, M. Rozet 

 had also, in 1828, placed below the old red sandstone; but in a 

 subsequent memoir, published in the Annates des Sciences Naturellcs 

 (xix. p. 145. 1830), he assigns it to the old red sandstone. At 

 the Meeting of the Geological Society of France at Boulogne, in 

 Sept. 1839, and at which some of the Fellows of the Geological So- 

 ciety of London assisted, the identification of the Boulonnais beds 

 with the Silurian system was fully admitted. When, however, doubts 

 were recently thrown out respecting the age of the formations in the 

 Liege districts on account of the nature of their fossils, Mr. Mur- 

 chison, who was present at the Boulogne Meeting, stated to the 

 author of this notice, that if the Liege country had been wrongly 

 identified, the older beds of the Boulonnais had been wrongly iden- 

 tified also. To determine the question, as far as fossils would assist, 

 Mr. Murchison procured, by the kind assistance of M. Dutertre 

 Yvart, a collection of specimens in the Museum at Boulogne. An 

 examination of these specimens with published lists, proved that the 

 inference was just, and that there exists in the Bas Boulonnais, the 

 same mixed assemblage of mountain limestone, Silurian and Devo- 

 nian, or peculiar fossils, as in the province of Liege and in Devon- 

 shire. 



Nov. 4.— A paper was read on Glaciers, and the evidence of their 

 having once existed in Scotland, Ireland, and England, by Professor 

 Agassiz, of Neuchatel. 



M. Agassiz commences by observing, that the study of glaciers is 

 not new, as Scheucher visited, and even drew, most of the glaciers 

 of Switzerland; and as, at a later period, Gruner and De Saussure 



