INDEX. 
433 
Observatory of the Cape of Good Hope. Pendulum observations made there for determining 
the earth’s compression, 153. 
Optics. On the manufacture of glass for optical purposes, 1. 
P. 
Pacific Ocean. Determination of its relative height above the Atlantic at Panama, 59. 
Panama. Relative height of the Pacific and Atlantic at the Isthmus, 59. 
Pendulum. Observations at the Cape of Good Hope for determining the compression of 
the earth, 153. 
Investigations relative to the pendulum, 201. 
- Observations at Greenwich and Altona to determine the difference in the number 
of vibrations at these two places, 239. 
Physical astronomy. Researches in, 327. 
Plates ( transparent ). On the action of their second surfaces upon light, 145. 
Polarization of light by reflexion, 69. 
by refraction, 133. 
{elliptic), 287. 
Pressure. Its influence in producing double refraction, 87. 
Pyrometer {register-). A new one for measuring the expansion of solids, and determining 
the higher degrees of temperature upon the common thermometric scale, 257. 
R. 
Ref exion of light producing polarization, 69. 
Refraction {double). On its production by pressure, 87. 
Laws of the polarization of light by refraction, 133. 
Ritchie (William, A.M.) On the elasticity of threads of glass, with some of the most 
useful applications of this property to torsion balances, 215. 
S. 
Sabine (Capt. Edward, R.A. Sec. R.S.). Note on the Rev. F. Fallows’s observations 
with the pendulum at the Cape of Good Hope, 175. 
Experiments to determine the difference in the 
number of vibrations made by an invariable pendulum at Greenwich and Altona, 239. 
■■ — — Experiments to ascertain the correction for 
variations of temperature, within the limits of the natural temperature of the South of 
England, of the invariable pendulum recently employed by British observers, 251. 
Seco?id surfaces of transparent plates. Their action upon light, 145. 
Siamese twins {united). Account of them, 177. 
Simons (Dr.). Observations on the velocity of sound, 209. 
Sound. Investigations relative to its velocity, 209. 
