324 OBSERVATIONS OF THE MAGNETIC DIP 



Remarks: — Weather cloudy, strong south-east wind. The temperature 

 during- the observations from 60° to 59°. 



XIX. Magnetic Dip at Juliet, Illinois. Latitude 41° 30' N.; Longitude 88° 9' W. 

 Place of observation in the oak grove, near the church upon the hill, on the 

 west side of Illinois and Chicago Canal. 



Date. Hour. Needle No. 1. Needle No. 2. 



1841, Sept. 26, 2i— 4|, A. M. Observed dip, Poles direct, 72° 21'.92 72° 10'.18 



'• " " Poles reversed, 9 .55 22 .30 



Mean dip, 72 15 .73 72 16 .24 



Mean dip of both needles, 72 15.98 



Remar'ks: — Weather clear, light west wind. The temperature during the 

 observations from 64° to 62°. 



XX. Magnetic Dip at Ottawa, Illinois. Latitude 41° 15' N.; Longitude 88° 50' TV. 

 Place of observation a quarter of a mile west of the town, near the wooden 

 bridge, on the right bank of the creek, which consists of a soft sand stone. 



Date. Hour. Needle No. 1. Needle No. 2. 



1841, Sept. 29, 8— 11|, A. M. Observed dip, Poles direct, 72° 14'.12 72° 23'. 38 



" " «« Poles reversed, 27.40 16.08 



Mean dip, 72 20 .76 72 19 .73 



Mean dip of both needles, 72 20 .24 

 Remarks: — Weather cloudy, sun shining at intervals, brisk north-west wind. 

 The temperature during the observations from 44° to 56°. 



XXI. Magnetic Dip at Peru, Illinois. Latitude 41° 13' N.; Longitude 89° 3' W. 

 Place of observation on the immediate right bank of Illinois River, in a wil- 

 low grove, about eighty yards from the lower end of the town. 



Date. Hour. Needle No. 1. Needle No, 2. 



1841, Sept. 30, U—H, P. M. Observed dip, Poles direct, 71° 51'.20 71° 46'.22 



" " " , Poles reversed, 48 .35 54 .82 



Mean dip, 71 49 .77 71 50 .52 



Mean dip of both needles, 71 50 .14 



Remarks: — Clouds gathering to the west, and the air almost calm at the 

 beginning of the observation of Needle No. 1 ; north-west wind rises brisk and 

 strong at intervals, needle restless; its positions are measured by means of its 

 shortest vibrations. Calm weather succeeded again towards the close of the 

 observation of needle No. 1, but, being afraid of being disturbed again by simi- 



