86 PROGRESS OF SCIENCE. 



G. But Roger Bacon was not a Mathematician, a Chemist, 

 a Physicist only, he was also an ASTRONOMER, for we have 

 an uncontested proof of his knowledge in astronomy, and that 

 is the reform of the Calendar to which allusion has already 

 been made. In " Specula Mathematical he devotes a whole 

 chapter to this important subject. 



The Calendar. " The defects of the Calendar/' says he, 

 " have become intolerable to the sage and are in horror to 

 the astronomer. Since Julius Caesar's time, and in spite of 

 the corrections which have been tried by the Council of 

 Nicaia, Eusebius, Victorinus, Cyrillus, Bede, the errors have 

 become only more aggravated ; they have their origin in 

 the evaluation of the year, which Caesar believed to be 

 365 J- days, which every four years brings in the intercalation 

 of an entire day ; but this evaluation is exaggerated, and 

 astronomy enables us to know that the length of the solar 

 year is less by T^th of a day (about 1 1 minutes) ; thence it 

 happens that at the end of 130 years,* one day in excess 

 has been reckoned, and this error would be corrected if one 

 day was cut off after that period. 



"The Church had at first fixed the Spring Equinox on 

 the 25th of March, and now on the 2ist; but the Equinox 

 does not arrive at that date. This year (1267), the Equinox 

 has come on the I3th of March, and every 125 years or 

 thereabouts it will come sooner by one day. The Church 

 was mistaken from the first : 140 years after the Incarnation 

 Ptolemy found that the Equinox came on the 22nd of 

 March; that was 1127 years ago. It now comes on the 

 I3th, that is 9 days sooner, and by dividing 1127 by 9,, 

 we obtain 125, which is the number of years at the end of 

 which the Equinoxes are advanced one day. The Church 

 pretends that the Winter Solstice fell on the day of the 

 Nativity of Jesus Christ, the 25th of December. That is 

 a mistake the verification of Ptolemy having fixed it on 

 the 22nd, in the year 140, it could not, in the year one, 

 be more than a little over one day later that is to say,, 

 between the 23rd and the 24th. 



" Nor could the Spring Equinox in the year one be on 

 * Jn reality, 128 years. 



