186 OBSERVATIONS OF THE MAGNETIC DIP IN THE UNITED STATES. 
Date. Hour. PouaRity, No. READINGS. Dip. 
1842, Sept. 10, 6—7 A. M. Mark up. 40 73 11.0 
“ “ iG Mark down. 40 72 54.0 
CC aCe « Mean result. 80 1B BA 
The following observations were made by myself with an instrument kindly loaned for 
this purpose by Prof. Bache, Superintendent of the United States Coast Survey. The 
place of observation was in the middle of the grove behind the Lunatic Asylum at Bloom- 
ingdale, about seven miles north of the City Hall of New York. 
Bloomingdale, Lat. 40° 49’, Long. 75° 57’ West. 
1859, June 11, 103 A. M.—3 P. M. Needle No. 1. 40 72 45.5 
“ & a6 Do. poles round. 40 60.2 
“ “ 6c Mean of No. 1. 80 52.9 
“ « “ Needle No. 2. 40 ‘ 44.8 
«“ “ GG Do. poles round. 40 56.5 
“ & “ Mean of No. 2. 80 50.7 
“ “ “ Needle No. 3. 40 86.3 
“ “ “ Do. poles round. 40 59.5 
“ “ “ Mean of No. 3. 80 47.9 
“ ‘“ “ Mean of three needles. 240 72 50.5 
These observations, compared with those heretofore made in this vicinity, indicate that 
the Dip of the needle at New York was decreasing from 1823 to 1846, since which time 
it has slightly increased. These results correspond tolerably well with those obtained at 
Hudson, Ohio, both as respects the time and amount of the change of Dip. 
