iv CONTENTS. 



Page 

 The Rev. Prof. Challis on the Method of Investigating generally 

 the partial Differential Equations applicable to the Motion of 



Fluids 84 



Mr. T. Galloway's Remarks on Fernel's Measure of a Degree 90 

 Mr. J. P. Joule on the Electric Origin of the Heat of Combus- 

 tion 98 



Prof. Maiden on the Development of the Cosines and Sines of 



Multiple Arcs , 113 



Prof. De Morgan's Additional Note on the History of Fernel's 



Measure of a Degree 116 



The Rev. D. Williams's Plausible Reasons and Positive Proofs, 

 showing that no Portion of the Devonian System can be of 



the age of the Old Red Sandstone 117 



Prof. De Morgan on the Invention of the Signs + and — ; and 

 on the sense in which the former was used by Leonardo da 



Vinci 135 



Prof. Encke's Ephemeris of the Periodical [Encke's] Comet, 

 1 842 ; and on the Mass of the Planet Mercury ; in an Extract 



from a Letter to Mr. Airy 137 



Notice of the Magnetometric, Geographical, Hydrographical 

 and Geological Discoveries or Observations made by the Ex- 

 pedition under the command of Capt. James C. Ross, R.N., 

 F.R.S. ; being extracts from a Despatch addressed to the Se- 

 cretary of the Admiralty 141 



Observations made at the Magnetic Observatory at Toronto, 

 during a remarkable Magnetic Disturbance on the 25th and 

 26th of September, 1841 ; with Postscripts, containing the 

 Observations of the same Disturbance made at the Magnetic 

 Observatories of Trevandrum, St. Helena, and the Cape of 



Good Hope 146 



Proceedings of the Royal Society 1 63 



Preparation and Composition of Sebacic Acid, by J. Redten- 



bacher 168 



Euchroic Acid 169 



Separation of Gold and Platina 171 



Lithofellic Acid 171 



On a new Arrangement of Instruments for observing Tempera- 

 tures and the Dew-point, by Mr. R. Adie 172 



Influence of Comets 174 



Vegetable and Animal Fibrin, Albumen, and Casein 174 



Meteorological Observations for December 1841 175 



Table 176 



NUMBER CXXX.— MARCH. 



Mr. H. Croft's Abstract of Dr. H. Kojip's Researches on the 

 Specific Weight of Chemical Compounds 177 



