COMMON THINGS THE ALMANACK. 



setting of celestial bodies. 53. Distortion produced by the atmos- 

 phere. 54. Other effects. 55. True and apparent sunrise. 

 56. The sun seen before it rises. 57. Conventional meaning of the 

 terms sunrise and sunset. 58. Refraction. 59. The Equinoxes 

 60. Day and night rarely of the same length. 61. How modified by 

 refraction. 



33. SINCE the dates of tlie corresponding phases of the real and 

 ecclesiastical moons never differ one from the other by more than 

 two days, and generally by still less, it happens most commonly 

 that the 14th of the paschal moon and the full of the real moon 

 fall in the same week, and in all such cases the date of Easter-day 

 would be the same, whether it be determined by the one moon or 

 the other. But they may and sometimes do fall in different 

 weeks. Thus the full of the real moon may fall on a Friday or 

 Saturday, while the 14th of the paschal moon falls on Sunday or 

 Monday. In that case the date of Easter determined by the 

 paschal moon will be a week later than if it were determined by 

 the real moon. 



On the other hand the 14th of the paschal moon may fall on 

 Friday or Saturday, while the full of the real moon falls on 

 Sunday or Monday. In that case the date of Easter, as 

 determined by the paschal moon, would be a week earlier than its 

 date determined by the real moon. 



; 34. "Whenever this discordance arises between the dates of 

 Easter, as it would be determined if the real moon presided over 

 it, and as it is determined by the ecclesiastical moon, the public 

 press teems with diatribes either against the astronomers for mis- 

 direction of the computers of the almanacs, or against the com- 

 puters for running counter to the lunar tables of the astronomers. 

 As examples of this may be mentioned the year 1798, in which by 

 the dictates of the real moon Easter should have fallen on the 

 1st April, but the ecclesiastical moon postponed it to the 8th ; the 

 year 1818, in which the real moon would have assigned it to the 

 29th March, but the ecclesiastical moon threw it back to the 

 22nd March, and the year 1845, in which the ecclesiastical moon 

 placed Easter on the 23rd March, while the real moon would have 

 postponed it to the 30th. 



35. It was on the last mentioned occasion that the questions 

 raised, and the disputes which prevailed, produced two remarkable 

 essays on the subject of the Calendar and its history, by Professor 

 De Morgan, which were published in the " Companion to the 

 British Almanack for the years 1845 and 1 846." In these articles 

 were for the first time exposed some glaring errors committed by 

 the British Legislature in the Act of Parliament (24 Geo. II,, 

 cap. 25, A.D, 1751), which at the time of the change of style 

 18 



