[ Vi ] 
I\. On the hues of the polarization of light by refraction. By David Brewster, 
LL.D. F.R.S. L. 8$ E, page 133 
X. On the action of the second surfaces of transparent plates upon light. By 
David Brewster, LL.D. F.R.S. L. 8$ E 145 
XI. Observations made with the invariable pendulum (No. 4, Jones), at the 
Royal Observatory, Cape of Good Hope, for the purpose of determining 
the compression of the earth. By the Rev. Fearon Fallows, F.R.S. 
Astronomer of the Cape Observatory. Communicated by the Lords Com- 
missioners of the Admiralty 153 
XII. Statement of the principal circumstances respecting the united Siamese 
Twins now exhibiting in London. By George Buckley Bolton, Esq., 
Member of the Royal College of Surgeons, and of the Medical and Cki- 
rurgical Society of London. Communicated by the President. . . 1 77 
XIII. On some properties in achromatic object-glasses applicable to the improve- 
ment of the microscope. By Joseph Jackson Lister, Esq. Communi- 
cated by Dr. Roget, Secretary of the Royal Society 187 
XIV. On the pendulum. By John William Lubbock, Esq. F.R.S. . . 201 
XV. On the theoretical investigations of the velocity of sound, as corrected from 
M. Dulong’s recent experiments, compared with the results of the obser- 
vations of Dr. Moll and Dr. Van Beek. By Dr. Simons, Assistant at 
the Observatory of the University of Utrecht. Communicated by Captain 
Henry Kater, Vice-President of the Royal Society 209 
XVI. On the elasticity of threads of glass, with some of the most useful appli- 
cations of this property to torsion balances. By William Ritchie, A.M. 
F.R.S., Rector of the Royal Academy of Tain 215 
Appendix. 
Mi t corob >gical Journal kept at the Apartments of the Royal Society, by order of 
the President and Council. 
