,4B- MEASUREMENT OF AN ARC 



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^"Cooty, to the time oF the experiments at Bcllary, which .was 24 

 -at the above rate 0,0048 feet, which deduced from 100,0119 :et,.iuc 

 length by -the, experiments at Bellaty, we fnali have the differer j: :?-I 

 ,0071 feet, aqd therefore 100,0071 feet for the length of the . .indarcl 

 chaia pTevious to-ihe raeafurement near Goofy, to which add ,01218 .• 

 which was the exeefsof the meafadng chain above the othe • ■-' 



time, the length of the meafaring chain was then 100,10928 feet, and 

 that muUiplied by 326, the number of chains meafared, will give 

 32606^2.853 feet, for the apparent length of the.bafeo But this is fup- 

 pofmg the increafe in the length of the ftandard chain to be uniform 

 which cannut have been the .cafe, becaufe ,1574 feet the excefs of the 

 fbndard chain above the brafs meafure in i8i;5, divided by 13, the 

 number of ^ears it has been in my poffeffion, will only give ,(^012. 

 feet for each year, which is only half of what is deduced, from the 

 -above rale; of ,0048 feet for two years. It i§ therefore more probable' 

 that for fome jears af|er the chain was in this country, it had remained • 

 unchanged, and that when the ruft; began to operate, it had lengthened 

 rapidly, btit where to mark the commencement it is impoffible to fay, 

 unlefs we date it about the lime when the irregularity was noticed ia 

 the comparative lengths, that is in the interval between the conclufion 

 of the bafe near Pallamcottak, and the commencement of that near 

 Goofy, and in order to make a corre^lion, the moft probable means will 

 l)e to fuppofe that the ftandard chain had lengthened thofe divifions 

 which appeared to be defe6live in the excefs of the meafuring chain 

 when the comparifon was made, previous to the meafurement near Goofy^ 

 viz. 8,63 divilions. Now 8,63 divifions is equal to ,00345 feet, therefore 

 if we fuppofe this to be the only lengthening from the ruft, and that the 

 meafuring chain had lengthened from ufe only, we mull in thaf cafe 

 iczili the iiandard chain 100,00345 feet, and this at the tempera 



