296 professor g. b. airy on the eclipses 
Central eclipse on the Northern position of Agathocles. The oval whose centre is 
on the line of Unvaried Elements is intended only to show^ the breadth of the 
shadow, which will be sensibly the same for each of the positions of central path. 
On examining these, the following remarks will at once suggest themselves. 
41. If the centre of the shadow followed the line of Condition 1, the shadow would 
obscure no open country except a very small distance north-east of the Pisidian 
Mountains ; and even there the obscurity would be short. The western towns how- 
ever from Halicarnassus to Pergamum would be shaded. 
If the centre followed the line corresponding to a central eclipse for the Southern 
position of Agathocles, the shadow would be almost central at what was afterwards 
Antioch, Celsenm and Pergamum ; and there would be a great total eclipse at Issus 
and Tarsus, and on all the western towns from Ephesus to Troy ; and the southern 
plain of Iconium would be in the shade. But Csesarea, Melitene, Ancyra, would be 
'""ifthe centre followed the line of Condition 3, Issus, Tarsus, and a great length of 
the southern road, would be covered; but the shadow would not extend to Csesarea, 
Ancyra, or Melitene. Sardes would now be out of the shadow. 
If the centre followed the line corresponding to central eclipse for the Northern 
position of Agathocles, Issus, Tarsus, Csesarea, Iconium, would be within the 
shadow ; Melitene, Pergamum, Ancyra, would be in light. Generally, the centre o 
the peninsula would be in shade. , aa 
If the central point followed the line of Condition 4, Melitene would be shaded; 
Csesarea and Ancyra would be nearly in the middle of the shadow ; and the northern 
plains would be covered ; but the plain of Iconium and the whole western coast 
south of Lainpsacns would be free from shade. .r. j-- 
42. Any one of these tracks of the shadow (perhaps excepting that of Condition 1) 
is compatible with a conceivable place of engagement. In balancing the probabilities, 
we must in some measure be guided by the extent of ground proper for large military 
operations which the total shadow would cover. J udging thus, I should fix on a course 
between that of Condition 3 and that corresponding to central eclipse at the North 
position of Agathocles as most probable. This selection, it will be remarked, ex- 
cludes the possibility of Agathocles being at the South position; and theijfore it 
adopted, would decide absolutely that Agathocles sailed on the north side of Sicily. 
43. If in conformity with this selection we suppose that the Unvaried Argument 
of Latitude ought to be increased by 1-53 X variation of 20\ or by 30' 60", and if we 
remark that the interval of time from 1782, when Damoiseau’s epoch is nearly correct, 
is -23-66 centuries, it will appear that the secular motion of argument of latituue 
ouo-ht to be diminished by P 29" or 42" nearly. Assuming our motion of mean lon- 
gitude to be correct, the same correction ought to be applied to the regression ot tie 
node. This makes the secular regression of the node for a Julian century equal to 
134° 8' 13" which is rather less than the smallest of those found by other iiives- 
