[ 2 43 ] 
The reafon of this will be plain, when we confider, 
that 1 8 degrees from either of the nodes of the 
Moon’s orbit is the greateft diftance, at which her 
Shadow can touch the earth at either of its poles. 
And as there are 18 degrees on each fide of the 
node, within the limits of a lolar eclipfe > and twice 
1 8 make 36, thefe are all of the 360 degrees of the 
Moon’s orbit about either of the nodes, within which 
there can be an eclipfe of the Sun : and as thefe eclipfes 
fhift through 28 minutes 12 feconds of thefe 36 de- 
grees, in every Chaldean or Plinian period, they will 
fhift through the whole limit in 77 periods, which 
include 1388 years and 3 months. And then, the 
periods have the remaining 324 degrees of the Moon’s 
orbit to fhift through, at the rate of only 28 minutes 
1 2 feconds of a degree in each period, before they 
can be near enough to the fame node again, for the 
Moon’s fhadow to touch the earth ; and this cannot 
be gone through in lefs than 12,492 years: for, as 
36 is to 1,388, fo is 324 to 12,492. 
The eclipfe, April iff, 1764, fell in the open fpace,' 
quite clear of the earth at each return, ever fince the 
creation till A. D. 1295, June 1 3th old ftile, at i2 h 
52' 59" p. m. when it firft touched the earth at the 
north pole, according to the mean (or fuppofed e- 
quable) motions of the Sun and Moon j their con- 
junction being then 17° 48' 27" from the moon’s a- 
feending node, in the northern part of her orbit. 
In each period fince that time, the conjunction of the 
Sun and Moon has been 28' 12" nearer and nearer 
the fame node, and the Moon’s fhadow has therefore 
gone more and more foutherly over the earth. In the 
year 1962, July 1 8th, old ftile, at io h 36' 21 " p.m. 
K k 2 the 
