Page:Popular Science Monthly Volume 18.djvu/787

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year brings back computed time 24 21·6 2·4 hours behind real time. To lose a whole day at this rate will require 10 400 4,000 years.

This arrangement seems simple enough to us now, but it required a convention of astronomers, summoned to Rome for this purpose, ten years to effect the adjustment. This is called the change from Old to New Style. It also changed the dominical letter, which occurred in this wise:

The dominical letter of 1582 was G, and, A being always the letter for the 1st of October, that day must have been Monday, and in regular order the 17th would have been Tuesday, whose letter was C. The change was made by calling the 5th day, which was Friday, the 15th, whence Saturday became the 16th and Sunday the 17th, whose letter we have just seen was C, whence C instead of G became the dominical letter for that year, N. S., and by this all subsequent Sunday letters were regulated. C is the fourth letter in backward order from G, hence the dominical letter of any year, N. S., was four letters backward from the letter belonging to that year O. S., and remained so until 1700, after which IST, S. is but the third letter from O. S. because, according to N. S., 1700 is not a leap-year and has but one dominical letter. In O. S. it would be leap-year, and would have two letters. For the same reason, after 1800 N. S. it is only the second letter backward from O. S., after 1900 only the first backward, and so continues until 2100—the year 2000 making no difference, as it is a leap-year in both styles. After 2100, Sunday letter N. S. is the same as that of O. S., and gains one letter each succeeding century, except those which are multiples of four hundred, so that, in every nine hundred years after 2100, the N. S. and O. S. Sunday letter correspond. This furnishes a perpetual almanac.

This arrangement of the calendar, whose complete cycle is four hundred years, is called the Gregorian, from the name of Pope Gregory, through whose instrumentality it was made. It was adopted shortly afterward by all the Catholic countries of Europe; but Protestant countries refused to adopt it, notwithstanding its obvious superiority and correctness, because it was originated by Catholics. Enlightened public sentiment compelled its adoption in course of time, and an act was accordingly passed by the British Parliament in 1752, almost two centuries later, ordering that the 3d of September should be called the 14th, the error having by that time amounted to eleven days. The change was, however, not popular among the masses, because it changed the time of long-established festivals, and members of Parliament were insulted in the streets by the rabble calling after them: "What have you done with the days?" "Give us back the days you stole!"

We have already seen that tables were constructed showing on what days each new moon would fall in the whole lunar cycle, but,