Notes on the Life of Arago. 59 



and particularly on the Refracting Powers of different Gases." 

 With M. Petit, Arago investigated " The Refractive Powers 

 of certain Liquids, and of the Vapours formed from them. 

 With Fresnel, he examined " The Action which the Rays of 

 Polarized Light exercise upon each other :" — and on those 

 subjects much valuable matter will be found in his Memoirs. 

 Omitting from our list those Astronomical notices which 

 regularly appeared in the Annuaire — and which, though 

 forming a part of his official duty, manifest, nevertheless, the 

 zeal of the Secretary and subsequent Director of the Bureau 

 des Longitudes — we would refer to M. Arago's memoirs " On 

 the Comets of Short Period ;" " On the Pendulums of MM. 

 Breguet;" "On Chronometers;" " On the Double Stars;" 

 and on the vexed question, " Does the moon exercise any 

 appreciable Influence on our Atmosphere V 1 Passing from 

 astronomical subjects, we find several memoirs : — " On Noc- 

 turnal Radiation ;" " The Theory of the Formation of Dew ;" 

 and on allied subjects — as " The Utility of the Mats with 

 which Gardeners cover their Plants by Night;" "On the 

 Artificial Formation of Ice ;" and " On the Fogs which form 

 after the setting of the Sun, when the Evening is calm and 

 serene, on the Borders of Lakes and Rivers." Indeed, the 

 whole of the phenomena to which Dr Wells had directed at- 

 tention in his excellent work " On Dew," was thoroughly 

 investigated by M. Arago. 



When we add the memoirs on " The Ancient Relation of 

 the Different Chains of Mountains in Europe, 1 '' " The Abso- 

 lute Height of the most Remarkable Ridges of the Cordilleras 

 of the Andes," " Historical Notices of the Steam-Engine," 

 " On Explosions of Steam-Boilers," " Historical Notices of 

 the Voltaic Pile," " those which are connected with the Po- 

 larization of Light," " the Phenomena of Magnetic Rotation," 

 and " On the Egyptian Hieroglyphics," we think we indicate 

 labours of a most varied and important character. 



For many years, M. Arago, who was the Director of the 

 Observatory at Paris, employed his position in the Chamber 

 of Deputies and elsewhere, to obtain large grants from the 

 state for the use of the institution over which he presided. 

 M. Arago, on the 13th September 1852, proposed to the Aca- 



