BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 553 



Kerschel, W.: Synopsis of the Writings of— Coutinuetl. 



A. D. Vol. p. 



1794 64 Gl I take tho meau of the first two, lO'i IG'" 15\5, for the approximate 



rotation period. 

 fi"2-3 Tables for the motion of the equator of Saiurn. 

 04-5 Comparison of observation witli the tables. 



Gj We may eouclude that tlu; period is exaet to ^^2™, and we need not 

 hesitate to llx the I'otatiou oi Saturn u[)on its axis as 10'' IG'" (t>*.4. 



Wm. IIeiisciiel. 

 [Dated] Slougli, near Windsor, Jan. 2'2, 1872. 



1795 85 4G Ontlie Nature and Construction of the Sun and Fired Stars. By William 



Hersciiel, LL. D., F. R. S. Read December 18, 1794. 

 4G The sun is the celestial body which should first attract our notice, 

 not only on its own account but since the fixed stars are, by tho 

 strictest analogy, similar bodies. 



46 Newtox has shown that the sun retains the jilanets of our system in 



their orbits ; 



47 Bradley has assigned tho velocity of the solar light; Galileo, 



ScuEiXER, Hevelius, Cassixi and others have ascertained its rota- 

 tion and the place of its e([uator. The Transit of Venus has given 

 means to calculate its distance, its real diameter, magnitude, density, 

 and the fall of heavy bodies on its surface. Thus we have already 

 a clear idea of the powerful influence of the sun. 

 47 I should not woader if [considering what we know] we were induced 

 to think that nothing remained to be added ; and yet we are stiU 

 very ignorant in regard to the internal construction of the sun. 



47 The spots have been supposed to be solid bodies, the smoke of vol- 



canoes, the scum floating on an ocean of fluid matter, clouds, opaque 

 masses, and to be many other things. 



48 The sun itself has been caUed a globe of fire, though perhaps meta- 



phorically. 



48 The faculaj have been called luminous vapors, etc. 



48 The light of the sun itself has been supposed invisible and not to be 

 perceived except by reflection, though the proofs seem to me to 

 amount to no more than saying Ihat we cannot see when rays of 

 light do no •, enter the eye. But it is time now to profit by the obser- 

 vations we are in possession of. 



48 I have availed myself of the labors of preceding astronomers, but have 



been induced thereto by my own actual observation of the solar 

 phenooieua. 



49 Following is a short extract of my observations. In 1779 there was 



a spot on the sun, divided into two parts, the largest above 31,000 

 miles in diameter. Both together must have extended above 

 50,000. Tho idea of its being occasioned by a volcanic explosion 

 ought to be rejected. 



50 We have pretty good reason to believe that all tho planets emit light 



in some degree. 



50 Example of the illumination of the moon during an eclipse, which 



could not have been due to the light from the earth. 



51 Tho dark half of Venus has been seen by difterent persons. 



51 In regard to the large spot on the sun, I concluded that I viewed the 

 real solid body of the sun itself, of which we rarely see more than 

 its shining atmosphere. 



51 Description of a largo spot seen in 1783 : the spot was plainly depressed 

 below the surface of the sun. 



