Cambridge Philosophical Society. 447 



ing merely, but by a quantity admitting of measurement by bodily 

 comparison, viz. by the quantity of plane surface intercepted between 

 the diverging lines and abutting on the point of intersection, or by 

 the magnitude of the included angle. 



Professor Challis gave an account of a luminous appearance ob- 

 served at the time of the perihelion passage of Klinkerfue's comet. 



Professor Stokes read a paper on the Optical properties of Light 

 reflected from Crystals of Permanganate of Potash. The substance 

 of this paper is embodied in a paper on the Metallic Reflexion exhi- 

 bited by certain Non-metallic Bodies, published in the Philosophical 

 Magazine, vol. vi. p. 393. 



Dec. 12. — Professor Fisher read the first part of a paper, entitled 

 " Researches, Physiological and Pathological, on the Development 

 of the Vertebral System." 



After having explained what he meant by the term vertebral 

 system, he stated (and he illustrated what he described by drawings) 

 that the spinal marrow, at a particular stage of growth of the human 

 embryon, exhibits indications of segmental development correspond- 

 ing to that of the spinal column ; that is to say, that each of its 

 halves offers on its external surface a series of symmetrical spaces 

 defined by transverse lines, each of which spaces corresponds to the 

 roots of a single spinal nerve ; and again, that each half presents in 

 its internal structure, a double series, one anterior, the other poste- 

 rior, of symmetrical areas, two of which appeared to equal in extent 

 one of the external spaces just spoken of. Professor Fisher also 

 stated that the spinal marrow offers, at the period of development in 

 question, several other peculiarities, some of them bearing likewse 

 a segmental character ; but he reserved a detailed description of 

 them for a future communication. 



Feb. 27, 1854. — A paper was read by Professor Challis, entitled 

 " A direct Method of obtaining by Analysis the mean motions of the 

 apse and node of the Moon's Orbit." See Philosophical Magazine, 

 vol. vii. p. 278. 



Also a paper by Mr. J. B. Phear on some parts of the Geology 

 of Suffolk, particularly with reference to the A'^alley of the Gipping. 



The deposits which constitute what is often termed the glacial 

 formation, but which the present state of our knowledge hardly 

 allows us to designate by a name significant of a common origin, 

 present so much confusion to the inquirer, and impose upon him so 

 much laborious research by the extent and the unconnected character 

 of their distribution, that they have hitherto met with less attention 

 than their importance deserves. 



The county of Suffolk seems to be a district where a portion of 

 these deposits is manifcf^ted with more than usual distinctness, and 

 is capable of being studied with comparative facility. The county 

 is separated from Norfolk on the north by the well-marked valleys of 

 the Ouse and the Waveney, is bounded on the east and south by the 

 sea and valley of the Stour, and is bordered by chalk uplands on the 

 north-west ; the whole central portion is thickly covered with a mass 



