15 
Remarks on a Passage in Pappus . 
The bellmen are in general very stout and healthy : their 
hard labour requires very good sustenance of three substantial 
meals in the day. Tea, bread, butter, eggs, bacon, potatoes, 
and fish, are their common diet. They are not particularly 
addicted to spirituous liquors. A little is very necessary for 
them, and it would require a good deal to affect them much. 
I cannot conclude this paper, without repeating my best 
thanks to Mr Bald and Mr Souter, to whose kindness and libe- 
rality I am indebted for the greater part of the details intro- 
duced into this paper. 
Edinburgh, April 1821. 
Art. III . — Remarks on a Passage in the Mathematical Col- 
lections of Pappus , from which the Obliquity of the Ecliptic 
has been deduced. 
Eratosthenes, who was born 276 years before Christ, de- 
termined, by his own observations, that the obliquity of the 
ecliptic was 28° 51' 19"5. This quantity was adopted by 
Hipparchus, who lived about 100 years later, and even Ptolemy 
may be said to have used the same*. M. Delambre-|*, indeed, 
seems to think, that Ptolemy did not observe much himself ; 
but, although he lived about 400 years later than Eratosthenes, 
even this interval would only have diminished the angle by a 
very few minutes, which probably was too small a quantity to 
have been ascertained by the instruments then in use. These 
records, however, of ancient astronomy, have always been con- 
sidered as very important for ascertaining the variation of the 
angle, which the equator makes with the ecliptic ; but there is 
another, which gives a result wholly irreconcileable with them. 
This is found in Pappus’s Mathematical Collections, Book vh 
Theor. 35., and the obliquity derived from the data there de- 
tailed, is no more than 23° 29' 55". Now, Pappus lived, ac- 
cording to Suidas, under the elder Theodosius, and consequent- 
ly in the latter end of the fourth century from the Christian 
* Histoire de VAstronomie Ancienne, vol. i. p 87., 
f lb. Discours Preliminaire. 
