113 



in the limestone at Burdiehouse leads the author to inquire, whe- 

 ther there be any analogy between the two deposits: he thinks 

 they are similar ; not, however, that he believes there is a freshwater 

 formation at Halbeath, but because he is of opinion that there is 

 no ground for considering that such a formation exists at Burdie- 

 house, or that the strata there offer any exception to the usual 

 phenomena presented by coal formations ; that the bed of limestone 

 is not, as Dr Hibbert maintains, of lacustrine origin, but presents 

 only such characters as may be sufficiently accounted for on the 

 supposition of the coal-measures having been deposited in an estuary, 

 which is now the commonly received theory of the formation of 

 coal deposits in general. 



Dr Hibbert rests its lacustrine character on the absence ot ma- 

 rine shells ; and, in connection with that circumstance, on the abun- 

 dance of land plants ; the presence of what he conceives to be fresh- 

 water fishes ; and a great profasion of the shells of what he ca^s 

 a Cypris, one of those microscopic entomostraca which inhabit 



The author, on the other hand, m^ntains that the absence of ma- 

 rine shells is no proof, because it constantly happens that we find 

 beds of limestone in which not a trace of an organized body can be 

 found, alternating with others nearly whoUy composed of them. 

 That the same genera, and many of the same species of plants, are 

 found throughout the whole of the carboniferous series, from the 

 old red to the new red sandstone ; that there is no ground for con- 

 sidering any of the fishes to have belonged to fresh water, but that, 

 on the contrary, they are met with in the zechstein of Germany 

 and the magnesian limestone of England, and frequently in other 

 regular coal-formations; and that the shells of entomostraca are 

 by no means a conclusive proof, as the shell of the Cytherina, which 

 lives in sea water, cannot be distinguished from that of the Cypns. 



3. Professor Forbes verbally communicated to the Meeting, 

 that he had succeeded in proving the Circular Polariza- 

 tion of Heat, whether accompanied or unaccompanied by 

 Light; when polarized heat is made to undergo two 

 total reflections within a rhomb of rock-salt, the plane of 

 total reflection being inclined 45° to the plane of prjrai- 

 tive polarization. 



