Geological Society. 457 



independent of those which have been made, or may be made, di- 

 rectly on the pressure of aqueous vapour at different temperatures 

 near the freezing-point, both above and below it, very correct de- 

 terminations of the values of the quantities C, M, and M' can be 

 made, such determinations will lead to more correct evaluations 



of ~- and -— for aqueous vapour in contact in the one case with 



liquid water, and in the other with ice, than we at present possess. 

 Such determinations, we may presume further, would, if very trust- 

 worthily arrived at, conduce to the attainment of a more correct 

 estimate of the density of steam at the freezing-point (or at the 

 triple point) than we now possess. In fact, in connexion with the 

 subject which has been here under consideration, there are various 

 important quantities so connected that improved determinations of 

 one or more of them may lead to more correct evaluations of others. 



GEOLOGICAL SOCIETY. 



[Continued from p. 315.] 



May 14, 1873. — Joseph Prestwich, Esq., E.R.S., Vice-President, 

 in the Chair. 



The following communications were read : — 



1. "On the genus Palceocoryne, Duncan and Jenkins, and its affi- 

 nities." By P. Martin Duncan, M.B. Lond., E.R.S., V.P.G.S., Prof, 

 of Geology in King's College, London. 



In this paper the author referred to certain minute fossils from 

 the Carboniferous rocks of Scotland, described by himself and Mr. 

 Jenkins in a paper read before the Boyal Society, as belonging to 

 the Hydroida, and most nearly resembling the recent genus Bimeria, 

 Wright. He stated that numerous specimens since received from the 

 Geological Society of Scotland threw some further light on the 

 nature of these fossils, and showed especially that in all probability 

 the base is not really cellular, but that the cellular appearance is 

 produced by the growth of the real base of the polype over the cells 

 of the Fenestella on which it grows. The author further described 

 what he believed to be the mode of growth of this organism, as dis- 

 played in the new specimens. 



2. " Notes on Structure in the Chalk of the Yorkshire Wolds." 

 By J. R. Mortimer, Esq. 



In this paper the author described a peculiar structure observable 

 in chalk from Yorkshire and elsewhere, giving it a striated appear- 

 ance. This structure had been ascribed by Dr. Mackie and others 

 to slickensides. The author adduced reasons for doubting the 

 mechanical origin of these striations, and argued that they are of an 

 organic nature. He ascribed them to corals, and remarked that 

 similar striae occur in all limestone formations. 



