Benjamin Peirce. 177 
have its centre of gravity controlled by its primary, and that it 
must be supported by the satellites. The principles of the solu- 
tion were Sree in an article, published in “Gould’s Astro- 
nomical Journal” in 18 At different times in the following 
years some sortions sof his theoretical treatment of the problem 
were published. The mathematical concn ae ie a large num- 
I 
ber of narrow solid rings was admitted. In t ‘Memoirs of 
the National Academy of Sciences” he published, in 1866, the 
formulas for the potentials and attractions of a ring. is 
hy eo has peculiar interest, from the mode of development of 
the f 
The place of comets in the solar system was a subject of 
his thought even earlier than the rings of Saturn. The dis- 
cussions and the computation of orbits of various ge in the 
years 1846-1849, were followed in the latter year by an argu- 
ment that the comets must have always been parts of diss solar 
system. 
In 1859 he applied the mes of solar repulsion of the mat- 
ter of the comets’ tails the observed form of the tail of 
Donati’s comet, and edinced the strength of the repulsive 
forces that drove off the nebulous matter. The oie year he 
gave, in a letter to the Academy of Sciences, of Paris, twelve 
remarkable and suggestive theses on the physical soucbieaoin 
of come 
In 1861 he made a communication to this Academy, suggest: 
ing the meteors as a cause of the acceleration of the moon’s mean 
motion. The paper was not printed, and it does not appear 
whether he referred to the direct impact of the seas upon 
the moon, or to the resistance due to the action of the moon in 
turning the meteors ont of their paths. Probably he awaisded 
th causes, since each has the efféct, to a limited degree, of a 
resisting medium. 
In the last two years of his life he presented to this Academy 
several communications upon the internal structure of the earth, 
d the meteoric constitution of the universe. Especially in 
ence,” ey were given rather as a basis for criticism and dis- 
cussion a as fully proved. They are founded upon the the- 
ory 0 er, which is advocated ae Sir William ey fee aut 
rs. 
by their impact with the sun, produce the violent commotions 
of the sun’s surface. A portion of the earth’s heat comes from 
