264 Mr. Bowditch on the Longituite of Cambridge. 
Phe men of hess ative eBeetvitions: makes the differences 
meridians of Greenwich and Cambridge 44, 44’ 29"+1, varying but» 
} of a second from the preceding calculation. |The near agreement 
of these results may however be considered as wholly accidental, since. 
the number of observations is small, and the differences from each 
other above three minutes. Indeed no great accuracy is to be ex- 
pected by this method, unless the number of observations be very 
great, and the number of emersions and immersions nearly equal. In 
proof of this, I shall give the longitudes deduced from the emersions 
of the first, second, and third satellites, observed at Chelsea by the 
Rev. Mr. Payson, and publised in the first volume of the Memoirs 
of the American Academy of Arts and Sciences. These observations 
being reduced to the meridian of Cambridge by allowing 26 seconds © 
for the difference of meridians, give the longitude of Cambridge as in _ 
the following table. 
App. time. Longitude. 
h. 
1st Satellite 1779, April pa 103637 4 4607-8 
1779, May 8 8 56 53 4 45 401 
1779, May 15 10 51 41 4 43 -39°6 
1779, June 23 9 16 14 4 43 40°9 
2d Satellite 1779, May 29 857 384 443 54°6 
1779, June 30 8 38 49 4 42 50°2 
- 3d Satellite 1779, May 16 8 5354 441 42-1 
1779, May 2312 5214 4 41 574 
1779, June 28 8 
Mean 4 43.35°3 
__ The mean of these nine observations differs nearly 54 seconds ‘ 
from that of the former set. Hence we perceive the uncertainty of 
this kind of observations. These calculations were not examined 
with much care, as it was found that the results were not sufficiently 
exact to be used in the present computation. 
The longitude of Harvard Hall in Cambridge being 4h. 44! 297 
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