228 



February 22, 1864. 



Communications were made by Professor Cayley " On a Case of 

 the Involution of Cubic Curves," and " On the Theory of Involution." 



By Mr. Spencer " On Vitality." 



March 7, 1864. 



Communications were made by Mr. Harry Seeley — 



1. " On the Significance of the Succession of Rocks and Fossils." 



2. " On Pterodactyles, and on a new Species of Pterodactylas 

 machcerorhynchus," 



April 18, 1864. 



Communications were made by Mr. Rohrs "On the Strains and 

 Vibrations of Ordnance under the Action of Gunpowder." 



By Professor Cayley " On the Classification of Cubic Curves," 

 and "On Cubic Cones and Curves." 



May 2, 1864. 

 Communications were made by Mr. Harry Seeley — 



1. "Note on Palceobalcena Sedgwicki (nob.), a Whale from the 

 Oolite." 



2. " On the Fossil Birds of the Upper Greensand, Palceocolyntus 

 Barretti (nob.) and Pelargonis Sedgwicki (nob.)." 



3. " On the Osteology and Classification of Pterodactyles, Part II., 

 with descriptions of the new species P. Hopkinsi and P. Oiceni." 



May 16, IS 64. 



Papers were read by Professor De Morgan — 



1. "A Theorem relating to Neutral Series." 

 The theorem is as follows. If a — «, -\-a 2 — ... be a convergent 

 series which has the limiting form 1 — 14-1—..., and if a e be of 



