BiBLioGRArnv OF iiersciiel's writings. 553 



Herschel, W.: Synopsis ov the Wnrnxos or— Continnod. 

 A. D. Vul. r. 



1794 84 (jl I take the mean of tlie lirst two, 10'' Ifi™ liV.T), for the approximate 



rotation period. 

 ()2-3 Tables for the motion of the e(inator of Salnni. 

 G4-5 Comparison of observation with the tables. 



6o We m.iy concUide that the period is cxaet to j;2"', and we need not 

 hesitate to lix the rotation of Saturn npon its a:cis as 10'' IG'" O.4. 



Wm. Heusciiel. 

 [Dated] .Slon,i,^li, near Windsor, Jan. 22, 1872. 



1795 8.') 4^) On the Xadirc and Coiistniction of tlte Sun and Fired Stars. By William 



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



4G The sun is the celestial body which should lirst attract our notice. 

 u<jt only on its own account but since the fixed stars are, by the 

 strictest .analogy, similar bodies. 



4G Newtox has shown that the sun retains the planets of our system in 

 their orbits; 



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

 ScuEiNEii, Hevelius, Cassini and othera have ascertained its rota- 

 tion and the place of its equator. The Transit of Venus has given 

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

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

 a clear idea of the powerful influence of the sun. 



47 I should not wonder if [considering what we know] we were inducdd 

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

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



47 The spots have been sup^josed to be solid bodies, the smoke of \ol- 



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

 masses, and to bo many other things. 



48 The sun itself has been called a globe of lire, though perhaps meta- 



phorically. 



48 The faculai 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 that we cannot see when rays of 

 light do no' enter the eye. But it is timt; now to prolit by tlie obser- 

 vations we are in i>osse>:siou of. 



48 I have availed myself of the labors of preceding ast ronomers, but have 



been induced thereto by my own actual observation of the solar 

 phenomena. 



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. The idea of its being occasioned by a volcanic explosion 

 ought to be rejected. 



50 We have pretty good reason to believe that all the 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 The dark half of re^M.-* has been seen by dillerent persons. 



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

 real solid body of the sun its.df, of which we rarely see more than 

 its shining atmosphere. 



51 Descript ion of a large spot seen in 178J : the spot was plainly depressed 

 below the surface of the sun. 



