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Meofurement of a Bafe on Houn (low- Heath. 42(7- 



tinned there lome time ; but the weather becpralng rather 

 worie, it was utterly impolhble to Hiew their Majeflies tlie 

 nature of the operation,, by any progrefs that could at that 

 time be made in the work. 



After a continuance of unfavourable weather forfeveral days, 

 the operations were relumed at 9 h. A.M. of the 23d, when the 

 rods being compared were found flill to exceed the fl:andard by 

 one-thirtieth of an inch, and the tempereture now w^as 61°.. 

 Here it is to beobferved, that in our progrefs forward, an accu- 

 rate regifler had been all along kept of that point of each rod 

 correfponding to the center of the hypothenufal pickets, by 

 noting its diftance from either end, whereby the error of the 

 chain at each ftation was readily difcovered, at the fame time 

 that the revolutions of the three rods ferved to keep the account 

 of the toi:al meafurement. In order, therefore, that this me- 

 thod might be diftindly adhered to, it was judged proper to 

 pufh on the rod that lay over the tripod at N? 10. exactly forty- 

 five inches, to make good the deficiency of the firfl fifteeu. 

 coincident rods, and that the account might be kept from the 

 lower end of the bafe in entire rods of 243, and complete 

 revolutions of 729 inches each. This being done, the reft 

 were placed in the ordinary fucceffion ; and we finifhed the 

 buiinefs of the day at the eighteenth flatlon, where the rods 

 being compared at 6 h. P.M. their mean length was found to 

 exceed that of the flandard ^'.^th part of an inch,- the tempera-- 

 ture then being 54". 



On Saturday the 24th of July, 'the rods were three times 

 compared; at 7 h. 30^ A.M., 11 h. 15^ A.M., and 5h. 45' P.M. 

 Th^ir mean excefs above the ftandard was found to be one- 

 thirtieth of an inch, and the mean heat 64°, In the courfe of 

 the. day, the jneafuremeut was continued irona the eighteenth to 



the. 



