Variation and Dip of the Magnetic Needle. 299 
Years. Variation at Boston. Falmouth. Penobscot. 
1745 Cate oye Gt 8° 49 
1750 7 42 8 27 8 35 
1757 7 20 Obs. os 6 8.58 
os, 2461 (fey ‘= 8 0 Obs 
1763 7. 0 Obs. 7 A5 Obs 7... 63 
1770 6 46 ese | 7°39 
1775 6 32 ES Te E26 
1780 6 18 je y Sac BS 
1785 6 A 6 A9 6.67 
1790 5 50 6. 35 6 43 
1795 5. 36 6 21 6 29 
1800 5 22 a 6. 1h 
The table which is given in Ames’s Almanac for 1771, is ex- 
actly like the preceding, with six exceptions, viz. the variations 
for Boston are given 9° 45’ for 9° 46’; 8° 57’ for 8° 51’; 6° 457 
for 6° 46’; and 5° 35’ for 5° 36’. In the column for Falmouth 
is given 10° 12’ for 10° 17’, and in the column for Penobscot 8° 
32’ for 8° 35’. I have no doubt that these were typographical 
errors in the almanac, and that the sheet in the possession of Mr. 
Adam Winthrop, which was doubtless printed under the eye of 
Prof. Winthrop, is the correct copy. It is evident that the prece- 
ding table was entirely computed, with the exception of those 
numbers marked Obs. For (1.) the table was published before 
1771. One quarter of the numbers were then certainly compu- 
ted. (2.) The variations for Falmouth are constantly 45’ greater 
than those for Boston, and those for Penobscot 8’ greater than 
those for Falmouth. Tio one who has ever made magnetic ob- 
servations, this will amount to an absolute demonstration t 
those numbers were never observed. (3.) The observations from 
1700 to 1800, with the exception of those marked Ods., all occur 
at intervals of five years, and the change of declination for this 
period is constantly 14’ or 15’. The observations of 1742 and 
1763, showing a change of one degree in 21 years, or somewhat 
more than 14/ in five years, doubtless furnished the data for the 
table. (4.) Penobscot and Falmouth, during the first years con- 
tained in the table, were small settlements. Penobscot was little 
more than a military post, and Falmouth was devastated by the 
Indians in 1692, and the town entirely broken up. ‘The inhabit- 
ants did not return until about 1708. Who then is this indefati- 
