On the Magnitude of the Year. V5 



into an horizontal direction. I flatter myself that 1 shall be able 

 to suggest such alterations in the process, as will prevent the 

 diffusion of the noxious poisons. 



N. B. Mr. S. recommends that fish, as soon as practicable 

 after taken, should be a little rubbed with salt, and laid upon a 

 ■loping board to drain, and when dry to be dipped in the acid 

 as before stated. The ham sent has been cured a year, and not 

 kept in a place very favourable for preservation. It must not be 

 soaked in water, previous to being cooked. One great advan- 

 tage attending this mode of curing hams or beef is, that when 

 hung up they are never attacked by the flies. 



III. On the Magnitude of the Year. By Mr. Yjeates. 

 To Mr. Tilloch. 



Sir, — X H E space of time between the sun's passage from one 

 solstitial point to the same again, is called a tropical or solar 

 year, and also the space of time between the sun's passage from 

 one equinoctial point to the same again ; which year has a re- 

 gard to the seasons, and marks their annual progress, and re- 

 turn : — and the space of time elapsed between the sun's apparent 

 motion from one fixed star to the same star again, is called a 

 sidereal year. 



The ancient astronomers did not distinguish the tropical from 

 the sidereal year with any precision until the time of Hipparchus, 

 who is said first to have discovered the sidereal year to be greater 

 than the solar year ; and who concluded from thence, that the 

 stars had a slow annual motion of their own from west to east. 

 This discovery laid the foundation for the doctrine of the pre- 

 cession of the equinoxes, which is one of the profoundest parts of 

 astronomy. 



Copernicus relates two most ancient, observations on the mag- 

 nitude of the solar year at many years distance ; the one by 

 Hipparchus in the i77tli Egyptian year after the death of 

 Alexander the Great, and the other made by Ptolemy in the 

 463rd Egyptian year after ; which interval Ptolemy computed 

 at 285 Egyptian years, 70 days, 7 hours, and 12 minutes; in 

 which space of time his commentator reckons just 285 tro- 

 j)ical years, where an Egyptian year contains twelve months of 

 thirty days each, and five intercalary davs, and where both the 

 Egyptian year and day begin at noon; so that dividing 70 days, 

 7 bours, 12 minutes, by 285, the quotient is 5 hours, 55 mi- 

 nutes, 12 seconds, and the solar or tropical year given at 365 

 days, 5 hours, 55 minutes, 12 seconds. After tliis method used 

 by Ptolemy, astronomers having made accurate observations 

 of the equinoxes, and computing the saujc at many years di- 

 stances, 



