

144 



M A T H E M A T I C A L and 



A letter from David Rillenhoufe, A. Ai, of Norriton^ to 

 JVilliam Smithy D\ D. Pro%)ojl of the college of Phila-- 

 delphia; containing obfervations of the COMET, 'which 

 appeared in June and fuly\ 1 770; ^ith the elements of 

 its motion^ and the Trajectory of its path. Communis 

 catcdto the Society ^ Augnjl 3//, 1770.- 



MLV. SIR, 



I fend you the f nil t of three or four 

 days labour^ during nx^hich I have covered many 



veral times, ft 



iifc. of the 



kflandft 



and I have no obje£lion to its being made public. 1 might-, 

 indeed, have been a little more careful to have the precif^ 

 time of my obfcrvations^ as the near approach of this Comet 

 required ten times the accuracy', that is neceffary for com-' 



futing the place of any planets I aU'^ hoivevert quite fatis- 

 fed that thefttuation Iha^s: given its orbit will be found 

 very near the truth, 



TH E circumftances moll remarkable in this comet were, 

 its prodigious apparent velocity, the fmallnefs of its 

 fize, and the lliortnefs of the time it continued vifible. Its 

 velocity was at firft furprifingly accelerated, and before it 



difappeared again retarded, from which its near approach 

 to the earth may be inferred. 



I did not fee it till Monday the 25th of June; and from 



its fituation at that time, I expected it would have been 

 vifible for many weeks, if not months; and therefore did 

 not prepare, with fuch expedition as I might have done, 

 for obfervlng its place with accuracy. But from the 27th 

 to the 30th, the weather continuing fair, every evening 

 about nine, I took the didance of the comet from Lucida 

 Lyra z^xiA LucidaAquiU^v^\\\\ a common Hadley's quadrant. 



i 



J 



At 10 



however, I faw both lucida lyra^ and the Cornet through 

 the clouds, and obferved their diftancc; but the comet 



was 



iT^ 



/ 



