96 



RECORD AND RESULTS OF 



Combining the deflections with the vibrations, we find — 



From first set A'= 4.286 and m = 0.3062 at 85= 

 From last set 4.2'79 0.3057 



Mean, 4.283 0.3060 



Fah. 



Magnet Z 1 suspended without ring 



No. of 

 vib'ns. 







20 



40 



60 



80 

 100 

 200 

 220 

 240 

 260 

 280 

 300 



12" 



4815 



14 



06.5 



15 



25.0 



16 



43.3 



18 



01.9 



19 



19.0 



25 



50.5 



2t 



10.5 



28 



28.3 



29 



46.5 



31 



05.0 



32 



23.6 



Temp. 



18° 



Extreme 



scale 

 readings. 



2Y0 

 and 

 330 



1S° 



286 

 and 

 315 



200 vibrations 



at 78°. 



13" 



02».0 

 04.0 

 03.3 

 03.2 

 03.1 

 04.6 



Observed time of 200 vib'ns, Y83'.37 

 Time of one vibration, 3.9168 



Correction for rate, — 0.0002 



3.9166 

 and vfhen corrected for torsion and 

 referred to 89°. T Fah. 



lgT^= 1.18702 



Mean 



U 



03.3T 



We find Igk^ = 0.63779 at 890.7 



Igk =0.19809 for Z 1 



IgmX = 0.00537 



X = 4.323 and j?i = 0.2342 at 89°. 7 Fah. 



man-net Z 1 



To compare the above values for the horizontal force with similar determinations at Washington, 

 I have given a complete table of results, as far as known to me. See U. S. Coast Survey Report 

 of 1861, Appendix N. 22, also Coast Survey Report of 1863. From my observations, in 1858, in 

 connection with Kane's Arctic Expedition, I deduce X= 4.255 ; and for 1862.5 we have the means 

 of the three values given above, or 4.296. 



Complete table of horizontal intensities determined at Washington, D. C. 



No. 



Year. 



Observer. 



Locality. 



X 



No. 



Year. 



Observer. 



Locality. 



X 



1 



1842.5 



Lefroy 



Capitol Grounds 



4.347 



10 



1856.7 



Schott 



Coast Sur. Office 



4.309 



2 



1844.5 



Locke 



Georgetown 



4.282 



11 



1856.7 





Capitol Grounds 



4.308 



3 



1844.5 



" 



Capitol Grounds 



4.313 



12 



1858.3 





Coast Sur. Office 



4.255 



4 



1844.5 



" 



Mag. Obs'y, Cpt. 



4.282 



13 



1859.6 







4.307 



5 



1845.2 



Lee 



Coast Sur. Office 



4.240 



14 



1860.7 







4.319 



6 



1845.9 



" 



" " " 



4.233 



15 



1862.5 







4.296 



7 



1851.5 



Dean 



Georgetown 



4.229 



16 



1862.6 







4.296 



8 



1855.7 



Schott 



Smithsonian Inst. 



4.338 



17 



1863.6 







4.282 



9 



1855.7 



" 



Georgetown 



4.250 













.-_ 





Mean 





1853.6 







4.287 









Mean, omitting Georgetown values 



4.295 



These values were determined with different instruments and magnets ; the A' at Georgetown 

 heights appears to be smaller than the Washington value proper (the two positions are 4 miles apart). 



