On the Constitution of Fkilipsite^ or Linie Harmotome, 375 



the presumptive evidence in favour of Neuropteris having been its foliage, 

 it is maintained, so far invalidates this supposition, and the internal 

 structure is considered to involve a powerful argument against it, inas- 

 much as the medullary sheath of >S'. elcgans, appears to be the analogue 

 of the regularly-netted cylinder of vascular tissue of some ferns {^c.fj. 

 Aspidhim Filix-mas). Accordingly, it is argued that the stem of this 

 species has the radially arranged ligneous zone of the Cycases super- 

 added to the vascular net-work of certain Ferns. The genus hiigiUaria 'm 

 therefore concluded to be essentially intermediate to the Vascular Cryp-. 

 togums and the Cycadeous Gymnosperms. 



On the Chemical Constitution of Philipsite or Lime Harmotome. 

 By Arthur Connell, Esq., F.R.S.E., Professor of Chemis- 

 try in the United College and University of St Andrews. 

 Communicated by the Author. 



The late researches of Kohler* appear to be sufficient to 

 shew that the constitution of the barytic and lime harmotome 

 cannot be expressed by the same chemical formula, on substi- 

 tuting lime for barytes. This conclusion follows principally 

 from his analysis of the barytic species, because that ex- 

 amination shews a complete conformity in the results of the 

 analysis of that species from three diiferent localities; 

 whereas the previous analyses differed materially from one 

 another ; my own, of the barytic harmotome of Strontiant 

 being the only one in nearly perfect accordance with Kohler's 

 result. We may therefore probably take the formula pro- 

 posed by Kohler, 2g-|s* + 7AS2-fl2 Aq. as representing 



the constitution of the barytic mineral. 



The exact constitution of the lime species is, however, not 

 so clear. The analysis of the lime harmotome of Marburg 

 and Kassel, given by Kohler, differs considerably from those 

 published by Gmelin and Hepel,t of this mineral, from the 

 former of these localities ; the oxygen of the one-atomed bases, 

 according to the first of these chemists, being 2.56, and, ac- 

 cording to the others, in one instance, 2.88, and in another, 



* Poggeud. Anual., xxxvii. 5C1. t Ed. New riiil. Jour., xiii. 33. 



t Annales de Mines, x. 355. 



