CONTENTS. 
——— 
NOTICES AND ABSTRACTS OF MISCELLANEOUS 
COMMUNICATIONS TO THE SECTIONS. 
MATHEMATICS AND PHYSICS. ~ 
Page 
Rey. T. Jarrett on Algebraic Equivalence....... seeeseoes itseaavacddcossecsarnese ae ee 
Professor Youne on Imaginary Zeros, &c...... snccuasauanseascee cree didacecaseaee Rasa 
Rey. C. Graves on Triplets......... Reseacdenacecere ratisese eos taceass ncaa vaeeretes ageeer es 
Mr. Grorce Boots on the Equation of Laplace’s Functions ........0...essceeee- 2 
Mr. H. Wepewoop on the Premises of Geometry...... Sam eecle seen Sear tend 2 
Sir Writram R. Hamitron’s Exposition of a System of Quaternions ......... 3 
Mr. F. Basurortu’s Description of a Machine for finding the Numerical Roots 
of Equations, and tracing a variety of useful Curves ......scc.scesccecesssecencees 3 
Mr. Toomas Wrieur Hitt on a System of Numerical Notation ......... see i! 
Ear of Rosss on the Nebula 25 Herschel, or 61 of Messier’s Catalogue......... 4 
Professor SrevELty on the Projection of a Star on the Dark Limb of the Moon 
just before its Occultation ............ deaneasan spacex(gtentacivacseancnenssuscee Deaeanand 5 
Professor Henry on the Heat of the Solar Spots .........s..ssceseeessceccuscees Saat Shel 
M. Boceustawsx1’s Description of a Universal Stand applicable to the Use of 
Astronomical Telescopes ...... papsccenenaseas Boknesemtsdauvaveteewaceuscnuscndaensa des 6 
Professor Powe. on certain Points in the Elliptic Polarization of Light by 
Metallic Reflexion ...........ssseeesseees Bcnnoceusees octdcesencans «daa -2ceosSbes eccnecne 6 
Sir Davip Brewster on a New Polarity of Light, with an Examination of 
Mr. Airy’s Explanation of it on the Undulatory Theory...... tecadat stants ese amcantiey nt 
”s Notice of Two New Properties of the Retina ........... 28 
Professor CuHatuts on the Aberration of Light ............ nnatanyscenaed baie sbideh’eaer: el 
Mr. G. G. Sroxes on the Aberration of Light .............cceceeceeee a are p aon ee 
Professor ANDERSON on the Caustics produced by two Mirrors in Rotation... 9 
Sir Davip Brewster on the Rotation of Minute Crystals in the Cavities of 
BUGLE) .5.c0cc+050000 peeceeas eae veer nee Saba deer AAS AS SEE Ee 9 
on the Condition of Topaz subsequent to the formation of 
certain Classes of Cavities Within it .........cccsscseccsenseeeeeseetes agence abe seasee 9 
Rey. S. EarnsHaw on the Rings which surround the Image of a Star formed 
by the Object-glass of a Telescope .....0...+++e+- wceccapovascccccsonsncesens acchoctrc 10 
Sir Davip Brewsrer’s Improvement in the Method of taking Positive Talbo- 
_ types (Calotypes) .........00 Peicnctte Races seeaee sported aha th netoneee sdarassee 10 
_ Mr. Wit1am Tuomson on the Elementary Laws of Statical Electricity ..... . il 
_ Rev. H. Luoyp’s Remarks on the Periodicity of Magnetic Disturbances......... 12 
_ Mr. J. A. Broun on the Results of the Magnetic and Meteorological Observa- 
tions at General Sir Thomas M. Brisbane’s Observatory, at Makerstoun, in the 
15 
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