468 PROCEEDINGS OF THE AMERICAN ACADEMY 



If what Herschel did at Slough and at the Cape of Good Hope was 

 the greatest work of his life, it by no means fills out the measure of his 

 services even to astronomy. Among his miscellaneous contributions to 

 scientific journals and transactions we find such subjects as these : Oc- 

 cultation of the Stars ; Determination of Differences of Geographical 

 Longitude ; Parallax of the Fixed Stars ; Orbits of Binary Stars ; 

 Biela's Comet and the great Comet of 1843 ; Revision of the Constel- 

 lations ; Satellites of Uranus ; Variability of Stars ; Test Objects for 

 Telescopes ; Entrance Passages into the Pyramids of Gizeh ; and 

 upon each and all might be inscribed, Non tetigit quod non omavit. 



Astronomy has done much for geography, and it promises to do more 

 for geology, whenever the geologist shall have a moderate knowledge of 

 astronomy, or the astronomer interest himself in the wonders of geol- 

 ogy. Of various contributions which Herschel made to geology, two 

 may be particularized. 1. He discussed with Lyell the effect which the 

 position of the major axis of the earth's orbit might have on the com- 

 parative climates of the northern and southern hemispheres. 2. The 

 startling and irregular changes in one of the stars of the constella- 

 tion Argo, some of which came under his own inspection, suggested to 

 Herschel reflections on the possible fluctuations in solar heat, and the con- 

 sequent vicissitudes in the earth's history, which are worthy of the at- 

 tention of every thoughtful geologist. Moreover, the scientific powers 

 of Herschel were not confined to mathematics, chemistry, astronomy, 

 and geology, for occasionally he made excursions into the domains of 

 meteorology, magnetism, electricity, and general physics. 



However broad the field over which Herschel travelled as an original 

 investigator, he still found time to write elaborate treatises on special 

 subjects. In the Encyclopedia Metropolitana, he has handled the sub- 

 jects of Light and Sound in a masterly way. His contributions to this 

 work were published forty years ago, but nothing has been written since 

 in the English language that will supply their place, although the trea- 

 tise on Sound requires now numerous additions to bring it up to the 

 present state of the science of acoustics. The treatise on Light is rich 

 in illustrations, experimental, mathematical, and historical, and contains 

 an impartial presentation of the merits of the corpuscular and undula- 

 tory theories of light, and of the great services of Newton, Huyghens, 

 Young, and Fresnel. The English reader owes especial regard to 

 Herschel for his first introduction to Fresnel, the mathematical ex- 

 pounder of the undulatory theory of light; his scattered and tardily 



