ON. THE MERIDIAN. :d 



ad c\i?-in was then taken afide, and the raeafuring chain 

 )een laid along with the other, was compared with the mea- 

 nd exceeded it by 0,2297 inches. This chain was put afids 

 iidard chain a fecond time applied, and the arrow coincided 

 ne mark. ThemeamriDg chain v/asalfo compared a fecond 

 ere appeared no seniibie difference. From the eom-parifoa 



©f the two chains^ it appears that ^12^'] — ^034^=: ,1556 inches, or ,0163. 



feet, is the excefs of the nlealitriDg chain above the other. 1'he whols: 



of thefe operations were begun and completed while the mean temp©* 



latnre given by- the five thermoiiie'tersj- was. 72?V 



Now the expanfion of 100 feet of brafs due to one degree of i^^ 

 perature exceeds the expanfion of the new chain (according to former 

 experiments) due to one degree tejinperafurej by ,00495 inches, and 

 ibe fame chain meafored exadly 100 feet by the brafs flandard in Lon-. 

 don at the temperature of 50^, therefore (72'^ — 50°)><,00495 gives ,1089. 

 inches which the chain ought to have fallen fhort, had there been no 

 siltcration in its length. But it exceeded the brafs meafure by ,0341 in- 

 ches, therefore ,]io89-|-,og4i or,i43inches:=:sOii9 feet,is what the chain 

 ha-s lengthened, and this quantity would be fenfibiy the famCj were the 

 chain compared with the brafs flandard at the temperature of 50^, for 

 ,0119 ^*^^^ ®f ^^^ fo^ 22^ of change in temperature would only be con» 

 traded >ooooo!6 feef, a quantity altogether infenfible. Hence the flan- 

 dard chain from this meafurement may be conlidered equal 100,0119 

 feet at the temperature of 50^.. 



In the latter end of Odober 1814, about 19 months afterward^^ 

 another comparifon was made with the brafs flandard at Hydrabad and 

 inorder to cnfurc fiiU greater accuracy, inllead of ufi.ig magnifying glafr 



E. 



