60 Royal Society. 



of the varying circle in which the two spheres intersect each other 

 will be an ellipsoid, inscribed at once in both the cylinders, so 

 as to touch one cylinder along one ellipse of contact, and the 

 other cylinder along another such ellipse. And the same ellip- 

 soid may be generated as the locus of another varying circle, 

 which shall be the intersection of too other equal spheres sliding 

 within the same two cylinders of revolution, but with a connect- 

 ing line of centres which now moves parallel to another fxed 

 right line ; provided that the angle between these two fixed 

 lines, and the angle between the axes of the two cylinders, 

 have both one common pair of (internal and external) bisec- 

 tors, which will then coincide in direction with the greatest 

 and least axes of the ellipsoid, while the diameter of each of 

 the four sliding spheres is equal to the mean axis. In fact, 

 we have only to conceive (with the recent significations of the 

 letters), that four spheres, with the same common radius =6, 

 are described about the points l, m', and l', m, as centres ; 

 for then the first pair of spheres will cross each other in that 

 circular section of the ellipsoid which has ee' for a diameter; 

 and the second pair of spheres will cross in the circle of which 

 the diameter is e"e'"; after which the other conclusions above 

 stated will follow, from principles already laid down. 



[To be continued.] 



XII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from vol. xxxii. p. 541.] 



March 23, <Y") BSERVATI0NS on some Belemnites and other 

 1848. ^* fossil remains of Cephalopoda, discovered by Mr. 

 Reginald Neville Mantell, C.E., in the Oxford Clay, near Trowbridge 

 in Wiltshire." By Gideon Algernon Mantell, Esq., LL.D., F.R.S., 

 Vice-President of the Geological Society. 



The author states, that a line of railway now in progress of con- 

 struction to connect the large manufacturing town of Trowbridge 

 with the Great Western, being part of the Wilts, Somerset, and 

 Weymouth line, traverses extensive beds of the Oxford clay of the 

 same geological character as those at Christian-Malford in the same 

 county, which furnished the remarkable fossil cephalopods described 

 by Mr. Channing Pearce under the name of Belemnoteuthis, and by 

 Professor Owen (in a memoir which received the award of a Royal 

 Medal of this Society), as the animals to which the fossils commonly 

 known by the name of Belemnites belong. 



The son of the author, Mr. R. N. Mantell, being engaged in these 

 works under the eminent engineer Mr. Brunei, availed himself of the 

 opportunity to form an extensive and highly interesting collection of 



