64 Lovering and Bond on Magnetic Observations at Cambridge. 
these another extremely delicate instrument by which variations of 
the Vertical Force may be observed. Consequently, with his two 
instruments the changes of Dip may be calculated to a close approx- 
imation, though the absolute Dip remains unaffected by all the im- 
provements. In addition to the usual corrections applied to obser- 
vations made with the dipping-needle the precaution should be taken 
of observing the inclination in different azimuths and deducing the 
true dip from every set at right angles to each other. Mr. Fox has 
invented a dipping-needle Deflector which gives the dip and intensity 
by a statical principle and Mr. Lloyd has applied the same princi- 
ple to the simultaneous determination of the dip and intensity. Ob- 
servations with the Vertical Force Magnetometer commenced with 
us on the Term-day of March, 1841; but they do not enter into 
the plan of the present paper and any further notice of them or of 
the instruments is deferred till we come to the description of the 
new Magnetic Observatory. The Dip has been observed directly 
at Cambridge and the vicinity during the last four years at irregular 
intervals. The Dipping-needles used were of the best construc- 
tion, one of them made by Gambey, and the other, now in the pos- 
session of Major Graham, obtained from Troughton & Simms. The 
following Table gives the results with some old observations on the 
same element: 
Place. Date.| Dip. |Gambey two SAE Means, 
needles. lone needle. 
Cambridge|1780)69°51 |Dorchester|June 8|74° 20.3|74° 25.6|74° 23 
xe 1782/69 41 Cambridge HOW Wied 74 17.1 
OG 1783\69 41 ue “3 56 74 20.1) 74 20.1 
ane Oe SAL ac June 22\74 24. 74 24.7 
Mean for 1782\69 44) re alee an Al ane 
Ree ea pa ee Sept’. 6/74 22.574 11.5)74 17 
Cambridge |42°22'71°8 1841 
Dorchester |42 i9|71 4 13 May 9/74 35.5 74 35.1 
Mean for |1840 | 74 216 
* This observation was made by Professor Loomis. 
