Mcafurement of a Bcife on Houn flow- Heaths 4-2;^ 



iubfequent ones were forming. The clamps faftening the firil: 

 rod to its {lands being then detached, it was carried by tvvo 

 men and laid on the alternate fide of the third ; and fo on in 

 fucceffion, until fifteen rod lengths were meafured off, being 

 the half of the firft hjpothenufe. 



The time confumed in meafuring this (hort diftance of 300 

 feet was not lefs than five hours ; owing, as has been formerly 

 mentioned, to the confined nature of the apparatus for moving 

 therodson intocoincidence, which requiredfuch nicety in placing 

 the ftands, as could not be efieded until after feveral repeated 

 unfuccefsful trials. All the executive people were therefore of 

 opinion, that it would be proper to difcontinue this miode of 

 meafurement, at lead: until a more convenient apparatus could 

 be thought of for the purpofe ; and that, in the mean time, 

 we iliould proceed by the method of contacts, as the only al- 

 ternative we could for the prefent adopt*. 



The rods being accordingly placed in conta6l with each 

 other, we foon made greater progrefs, finifhing the operations 

 ©f the day at the middle of the fourth hypothenufe, where 

 the tripod, with its guard, was placed, to preferve the point of 

 commencement for theenfuing morning,. 



* Although I acquiefced in the change thiis become necefTary, yet it was with 

 much reluclance, becaufe it left undecided the contefled point, with regard to 

 coincidences and contafts. If we could have proceeded with the coincident rods 

 till eighty one lengths were meafured off, and then meafured back the fjme fpace 

 by placing eighty rods in contaft, the point would have been clearly fettled. For 

 if the termination of the eightieth rod agreed exaftly with the point of departure, 

 contafts being the moft expeditious would have been judged the beft method. On 

 the contrary, if the eightieth rod fell fhort of reaching the point of departure,- 

 there could have been no doubt, that the difference muft have aril'en from 

 butting one rod agalnft the other, whereby a certain fmall proportion of each 

 rod came to be loft in the aceount^ by being meafured twice overt 



Tha 



