vi CONTENTS. 
NOTICES AND ABSTRACTS 
OF 
MISCELLANEOUS COMMUNICATIONS TO THE SECTIONS. 
MATHEMATICS AND PHYSICS. 
MarTHeEmMartics. 
Page 
Rev. T. R. Roprnson’s Opening Address ......... deusvesiveapousdesasen Sterabevenaete 
Professor Booie on the Theory of Astronomical Observations, and on some 
related QuestionS ......cccscessssessscccscsencesssionssssss eddveasece setsbiscussoeessecas =D 
on certain Additions to the Integral Calculus .............0+6. aye 
Professor Curtis on a System of Geodetics and the Conjugate System, traced 
on the two Sheets of a Surface of Centres, with special reference to the Case 
in which the Surface of Centres consists of an Ellipsoid and a Confocal 
Hyperboloid ..... Sco ccdecsasnteceseeocteensbas ssh saesas nod sa¥itve it enbaaesaa¥es secseseee = 2 
Rev. Cuaries Graves on the Interpretation of certain Symbolic Formule and 
Extensions of Taylor’s Theorem ......... Gosbtoccces venvensubea aeasuses jstvdesiticcady (0d 
Sir W. R. Hamrztton on some Application of Quaternions to Cones of the 
Third DePre? ....:22.cccccccscecsoccsnccstsccaccectosscecsssueusdsbetwassesaedsccvescanesss 3 
on the Icosian Calculus .......sssesesesisensess ouabis ctarsct 3 
Mr. Commissioner HarcraveE on Infinite Angles and on the Principle of Mean 
MAES aeaccvarscecscstsenewritaces« dhassbondevass sts trecevsssavdiacnadeqedecenas att smermuawe 3 
Mr. Joun Pope Hennessy on the Origin ahd Elimination of Euclid’s “Re- — 
GUCtO ad Absurda Mi 455). sve cascus adv yarets tes sed enna ls teiod aegh qe vameaee Sdevcessisnesy yy 3 
Rev. Professor JELLETT on some General Propositions connected with the 
Theory of Attractions ......... Saeneodvastevstcaccedscenccauesesueates die danenqaacseneed 3 
Mr. T. Martin on certain Properties of the Radii of Curvature of Curves and 
Surfaces, and their Application to the Method of Polar Reciprocation......... 4 
Mr. B. A. Murray’s Demotstration that the Three Angles of every Triangle 
are equal to Two Right Angles............ssccssoessscees Spamea cane as ac esse cee waemineds 4 
Rev. G. Saumon on the Surface of Centres of an Ellipsoid j..scsessccccssecsiscsae | 4 
Lieut, Orpricat INSTRUMENTS. 
Sir Davip Brewster on the Centring of the Lenses of the phe et Object- 
Glasses of Microscopes «...... bebeassaceesscdiscsccctaies eveccesadarsacaseceetassscczeae | 4 
M. Léon Foucautrt on a new Polarizer, resulting from a Modification of the 
ESIOUPUOL INICOL et occe tw ouGs coat easceser se: soho eee Silas nosed a'ciarc’eodaveseetamten bintes-suee 5 
——-— on a Telescope Speculum of Silvered Glass ......--.-.-+++. rer 
Dr. J. H. Guapstone on the Colour of Salts in Solution, each Constituent of 
which is coloured ......... deudauscwevedccecasecececsctesccne cacteae stacemeeeanerercetenae 8 
—— on the Effects of Heat on the Colour of Dissolved Salts 8 
