114 



MATHEMATICAL and 



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favoured with an account of your obfervations of the late 

 tranftt of Mercury ^ if you made any, and of the late eclipfc 

 of the moon, I fhallbe obliged to you for the continuance 

 of your correfpondence, and am 



Sir, yours, &c. 



M 



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xount of the terrefrial meajurement of the difference of 

 longitude and latitude'^ betiveen the obfervatories of^ox 

 riton and Philadelphia. 



Y 



Tb/^^ American Philosophical Society, &c. 



GEN T L E M E N, 



GREEABLE to the appointment you made (at 



A 



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Mr. Rittenhoufe 



• 



id myfelf, furniflied with proper in- 

 Norriton early on Monday, July 



for the above fervice; and took to our afEftance two able 

 and experienced furveyors, viz. M 



Mr. 7# 



The firft: thing we did, was accu 



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rately to afcertain the variation of ourcompafs, which wc 



Mr. Rittenhouft 



We 



then carefully meafured our chain, and adjufted it to the 

 exaft ftandard of ^(i feet. In the execution of the work, 

 •whenever the inftrument was duly fet, each courfe was 

 taken ofF, and entered down feparately, by three different 

 perions, who likevnfe kept feparate accounts of all the 

 diftances, and fuperintended the ftretching of every chain, 

 and the levelling and plumbing It, whenever there was 

 any afcent or defcent in the road. 



July 4th. We finifhed the furvey ; and Mr. W-Clcan^ Mr. 



7# 



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ference of latitude and departure feparately on each courfe 

 and diftance to four or five decimal places; and there was 

 fo great an agreement in this part of the work, when exe- 

 cuted, that we had all the fame refults to a few links, and 

 the whole was at laft brought to agree in ty^xj figure, by 



comparing 





