358 OBSERVATIONS ON THE MAGNETIC DIP AND “DECLINATION. 
Observatory. We read the needles alternately, and a mean of all the observations, as 
made by us both, is given in the several results. 
The close coincidence which had been remarked in the results of the two needles of 
this instrument, and the great uniformity in the readings of both in the various positions 
assumed for a course of observations, determined us to observe, without intermission, for 
twenty-four consecutive hours, with a view not only to a close determination of the dip 
at this station, but also to ascertain its diurnal variation. 
184], June.29th.— Negpie No. 1. 
Polarity of No. of Time of 
Marked end. Readings. Observation. ‘Temperature. Dip observed. 
Ss 24. 8h. 49m., P.M. 82°.7 74° 20'.76 
N 24 10 28 72.9 74 LILES 
Dip, by forty-eight observations on needle No.1, .-. . . . . 74° 15'.94 
1841, June 30.—NEEDLE No. 2 
N 24 1h. 35m., A.M. 78°.9 74° 16'.47 
8 24 3 12 ne 1838 74° 16.11 
Dip, by forty-eight observations on needle No.2, . . . . . « 74° 16'.29 
Nerpie No. 2, REPEATED. 
Ss 24. 10h. 03m., A.M. 85°.5 74° 18'.82 
N 24 lt 14 2 88 .5 74° 23'.28 
Dip, by forty-eight observations on needle No. 2, second set, . . 74° 21.05 
NeeEp iE No. 1. 
N 24 Oh. 28m., P.M. 89° 74° 14'.65 
s 24. 1 38 # 92 74° 21’.86 
Dip, by forty-eight observations on needle No. 1, second set, . . 74° 18’.25 
NereEpue No. 1, REPEATED. 
Ss 24, 3h. 18m.,. P.M. S20 74° 23'.5 
N 24 4 20 a: 84. 74° 09'.45 
Dip, by forty-eight observations on needle No. 1, third set,. . . 74° 16'.42 
Neepie No. 2.—JuneE 30. 
N 24 5h. 02m., P.M. 83°.5 74° 18'.13 
Ss 24 6 18 = 81 74° 13'.53 
Dip, by forty-eight observations on needle No.2, third set, 2° 2 74" 1888 
RECAPITULATION OF THE FOREGOING OBSERVATIONS AT CAMBRIDGE. 
(peue—a6a1| no, of (roe s0h] or opetrntats on | of sbucrraions on [ifean of exch sto] | Dip | 
| Needle. of Needle, each needle, path needle, readings. by each needle. 
| June 0, 4 |§ Sh.18m Pat} Oh.25m rx] 742 20.702) a40 157.04 
Lane 30, 2 5 ‘ PS eta lect tbe a nal 74° 16/.29 
Fane 30 2 ; = ee AM. he Hoan ip a eed | 74° 21.05 
re go) 1 § ‘ 00. 0iaet- Rioters P.M. se ae ee 74° 181.25 | 
‘June 30,1 ; A Med oye 9 gaping et a mtg 74° 16'.47 | 
June 30, 2 ; i age at is ace ney - 53 | 74° 15'.88 Z 
