247 



fi-om it as easily and with as little assumption as from the other. It 

 is true the author has not endeavoured to give a closer approxima- 

 tion than that which M. Fresnel himself has exhibited to the vibra- 

 tions which are polarized in the plane of incidence ; but, as far as 

 the approxiniiition is carried, it gives precisely M. Fresnel's results. 

 The want of experiments by which to test even the formulae we do 

 possess, is a sufficient reason for delaying farther investigations, 

 which shall approach more nearly to the truth in all cases- In the 

 mean time, it is of the utmost importance that M. Fresnel's empi- 

 rical formula should be established, and his mechanical ones exa- 

 mined, by di£Perent processes. 



Monday^ 4fth March. 

 Dr HOPE, V. P., in the Chair. 

 The following Donations were presented : — 



Philosophical Transactions of the Royal Society of London for the 

 year 1838. Part 1. 



Proceedings of the Royal Society of London, 1837-38. Nos. 31, 

 32, 33, 34, and 35. 



Astronomical Observations made at the Royal Observatory, Green- 

 wich, in the year 1837, under the direction of George Biddell 

 Airy, Esq. M. A., Astronomer-Royal. 



B^ the Royal Society. 



Transactions of the Cambridge Philosophical Society. Volume vi. 

 Part 3. — By the Society. 



Astronomische Nachrichten, Nos. 355 to 864 — By Professor Schu- 

 macher. 



Annual Report of the Institution of Civil Engineers. Session 

 1839. — By the Institution. 



Comptes Rendus Hebdomadaires des Stances de I'Academie des 

 Sciences. 1839. 1" Semestre. Nos. 5, 6 — By the Academy. 



Journal of the Statistical Society of London, No. 10, for February. 

 — 13y tfie Society. 



The Quarterly Journal of Agriculture ; and the Prize-Essays and 

 Transactions of the Highland and Agricultural Society of Scot- 

 land, No. 44, for March 183!) — By the Society. 



A Geometrical Practical Treatise, named Pantometra, Longime- 

 tra, Planimetra, and Stereometra ; by Thomas Digges, Esq. 

 —By P. D. Handy side, M. D. 



