CONTENTS 
OF VOL. 158. 
I. The Bakerian Lecture. — Researches on Vanadium. By Henry E. Roscoe, B.A.. 
F.R.S. page 1 
II. Computation of the Lengths of the Waves of Light corresponding to the Lines in 
the Dispersion Spectrum measured by Kirchhoff. By George Biddell Airy, 
Astronomer Royal , F.R.S 29 
III. An Account of the Observations on the Great Nebula in Orion , made at Birr Castle, 
with the 3' feet and fS-feet Telescopes, between 1848 and 1867. With a drawing 
of the Nebula. By Lord Oxmantown. Communicated by the Earl of Rosse, 
K.P., F.R.S. 57 
IV. On the Curves which satisfy given Conditions. By Professor Cayley, F.R.S. . 7 5 
V. Second Memoir on the Curves which satisfy given Conditions ; the Principle of 
Correspondence. By Professor Cayley, F.R.S. 145 
VI. Addition to Memoir on the Resultant of a System of two Equations. By Professor 
Cayley, F.R.S. 173 
VII. On the Theory of Local Probability, applied to Straight Lines drawn at random in 
a plane ; the methods used being also extended to the proof of certain new Theorems 
in the Integral Calculus. By Morgan W. Crofton, B.A., of the Royal Military 
Academy, Woolwich ; late Professor of Natural Philosophy in the Queen's Univer- 
sity, Ireland. Communicated by Professor J. J. Sylvester, F.R.S. . . . 181 
VIII. On the Anatomy of Balsenoptera rostrata. By Alexander Carte, A.M., M.D. 
Univ. Dubl., F.R.C.S.I., M.R.I.A., F.L.S. Lond., Hon. Mem. Imp. Zool. and Bot. 
Soc. Vienna, &c., and Alexander Macalister, M.D., L.R.C.S.I., Demonstrator of 
Anatomy R.C.S. I. Communicated by W. H. Flower, F.R.S. .... 201 
IX. Researches on the Intimate Structure of the Brain . — Second Series. By J. Lock- 
hart Clarke, F.R.S., &c 263 
X. Notices of some Parts of the Surface of the Moon. By John Phillips, M.A., D.C.L., 
F.R.S., F.G.S., Professor of Geology in the University of Oxford . . . 333 
