Louis XVIII. was born in 1755; add the digits, and you have XVIII.
What is remarkable is, that this number 18 is double the number of the king to whom the law first applies, and is triple the number of the kings to whom it has applied.
Here is another curious calculation:—
Robespierre fell in 1794;
Napoleon in 1815, and Charles X. in 1830.
Now the remarkable fact in connexion with these dates is, that the sum of the digits composing them, added to the dates, gives the date of the fall of the successor. Robespierre fell in 1794; 1 + 7 + 9 + 4 = 21, 1794 + 21 = 1815, the date of the fall of Napoleon; 1 + 8 + 1 + 5 = 15, and 1815 + 15 = 1830, the date of the fall of Charles X.
There is a singular rule which has been supposed to determine the length of the reigning Pope's life, in the earlier half of a century. Add his number to that of his predecessor, to that add ten, and the result gives the year of his death.
Pius VII. succeeded Pius VI.; 6 + 7 = 13; add 10, and the sum is 23. Pius VII. died in 1823.
Leo XII. succeeded Pius VII.; 12 + 7 + 10 = 29; and Leo XII. died in 1829.
Pius VIII. succeeded Leo XII.; 8 + 12 + 10 = 30; and Pius VIII. died in 1830.
However, this calculation does not always apply.
Gregory XVI. ought to have died in 1834, but he did not actually vacate his see till 1846.
It is also well known that an ancient tradition forbids the hope of any of S. Peter's successors, pervenire ad annos Petri; i. e. to reign 25 years.
And it is a remarkable fact that all have vacated the throne before that time is complete; Pius IX. must not reign beyond 1871.
The Popes who have sat longest are
