282 REPORT ON THE DISCOVERY AND NAME 



the dedication, the confident opinion is expressed by Huyghens, 

 that this satellite, being the twelfth planetary body in the solar 

 system, fills up the number of bodies belonging to it, " quo majo- 

 rem post hac reperttim non iri, prope est ut confirmare audeam." 

 Such was the bold prediction adventured by Huyghens, on the 

 ground of the supposed admirable qualities of the number twelve. 

 In less than two centuries which have since elapsed, the number 

 of planetary bodies (if we allow two satellites to Neptune) has 

 been increased to thirty-eight, with a prospect of a future indefi- 

 nite multiplication, bounded only by the improvements which may 

 hereafter be made in the telescope. 



Huyghens's satellite is by far the brightest of the Satumian 

 o^roup, and the sixth in order from the primary. Its period is about 

 fifteen days twenty-two hours, and in the nomenclature adopted by 

 Sir John Herschel, the convenience of which has been so signally 

 shown on occasion of the present discovery, it has received the 

 name of Titan. 



Toward the end of October, 1671, Dominique Cassini discov- 

 ered the exterior satellite of the whole group, usually called the 

 fifth in number, but now ascertained to be the eighth in order 

 fi-om the primary.* This discovery was made at Paris with a 

 telescope of seventeen feet. It has a period of above seventy-nine 

 days, and is called by Sir John Herschel lapetiis. On the 23d of 

 December of the following year (1672), Cassini, making use of 

 telescopes of thirty-five and seventy feet in length, discovered what 

 used to be called the third satellite of Saturn ; being the fifth from 

 the primary. Its period is of four and a half days, and it is 

 called Rhea by Sir John Herschel.f In 1684, Cassini discovered 

 the fourth and fifth of the old enumeration, the third and fourth 



• Journal des Savons de TAn 1677, p. 88. t Bitlo de VAn 1686, p. 139. 



