Royal Society. 437 



with a view to the construction of an achromatic telescope with a 

 fluid concave lens, instead of the usual lens of flint glass. In a let- 

 ter addressed to the President. By P. Barlow, Esq. F.R.S. 



24. —On the structure and use of the capsulae renales. By Sir 

 Everard Home, Bart.V.P.R.S.— Abstract of a meteorological journal 

 kept at Benares in the years 1824, -25, and -26 ; with remarks. By 

 James Prinsep, Esq. Communicated by Dr. Roget. — Description 

 of a percussion rifle, igniting by a spring instead of a lock. By 

 Lieut.-Col. Miller, F.R.S.* 



31. Feb. 7. — An account of trigonometrical operations in the 

 years 1821, -22, and -23, for determining the difference of longitude 

 between the royal observatories of Paris and Greenwich. By Capt. 

 Henry Kater, V.P.R.S. 



14. — On the mode in which the nerves belonging to the organs- 

 of sense terminate. By Sir E. Home, Bart. V.P.R.S. — Experiments 

 on heated iron, in reference to the magnetic and electric fluids. 

 By William Ritchie, Esq. A.M. Rector of the Royal Academy of 

 Tain. Communicated by Captain Sabine. 



April 24. — A paper was read, containing An account of experi- 

 ments on the elastic curve. By B. Bevan, Esq. Communicated by 

 the President. 



In inquiries on the strength of materials, it is often desirable to 

 know the real nature of the curve assumed by a prismatic rod, when 

 acted upon by the weight of its own parts. This curve has generally 

 been stated to be the parabola ; but repeated observation has led 

 the author to doubt the accuracy of the theory from which this con- 

 clusion has been deduced; and with a view, therefore, to determine, 

 by direct trial, the real form of the curve, he instituted a series of 

 experiments on prismatic rods, of various substances, and of various 

 depths and lengths, some fixed at one end, and others supported at 

 both ends, in a horizontal position. In every instance he found the 

 actual curve to differ from a parabola, and the deviations in the se- 

 veral points examined were such as indicated a regular and deter- 

 minate species of curve. No modification of the exponent of the or- 

 der of the parabola was adequate to express the relation of the co- 

 ordinates with sufficient accuracy in all cases. He found, however, 

 after many trials, that the following formula, which is that of the 

 common hyperbola, gave a very near approximation in all practi- 

 cal cases, namely, Ax 2 + Bar = y* 



The accurate determination of the elastic curve is a subject -of 

 some importance in practical mechanics ; since the rules at present 

 used by mathematicians and engineers for determining the modulus 

 of elasticity of different materials, are founded upon the parabolic 

 theory, and must therefore be liable to error. 



May 1. — A paper was read, intitled, " A description of a verti- 

 cal floating collimator, and an account of its application to astro- 

 nomical observations, with a circle, and with a zenith telescope. 

 By Capt. Henry Kater, V.P.R.S. 



The construction of the instrument which forms the subject of 



* See Phil. Mag. and Annals, vol. iii. p. $77 > 



this 



