298 Variation and Dip of the Magnetic Needle. 
In the preceding enumeration, I have not included a table of 
magnetic variations which is given in Vol. xv1, page 63, of this 
Journal. This table professes to give the variation of the needle 
at intervals generally of five years, from 1673 to 1800, for Bos- 
ton, Falmouth, and Penobscot. I have rejected the table, be- 
cause I am satisfied it is a caleulated table. This assertion will 
sound strange to some, for I have more than once been referred to 
it by men of science, as a repository of exceedingly valuable ob- 
servations, and they seem never to have suspected that the obser- 
vations were not genuine. But there is no room for the shadow 
of a doubt, that those numbers were mostly calculated. The evi- 
dence is as follows: The table is a very old one, being found in 
the Almanac for 1771, by Nathaniel Ames. A copy of this al- 
manac is in possession of Mr. William Lyon, of New Haven. 
There is also in the possession of Mr. Adam Winthrop, of Lou- 
isiana, grandson of Prof. Winthrop of Harvard University, a 
small printed sheet, in the form of a handbill, containing the 
same table. It is without date, but bears marks of age, and was 
found among the papers of Prof. Winthrop. It is my opinion 
that this is the original from which the table in the almanac was 
copied, and as it is a document to which circumstances have given 
- considerable consequence, I have here transcribed it verbatim. 
“ A table, exhibiting the variation of the compass in Boston and 
the parts adjacent, from the earliest accounts of it to the end of 
the 18th century; agreeable to the actual Observations distin- 
guished by Obs. By John Winthrop, Esq., Hollisian Professor of 
Mathematics at Harvard College, in Cambridge, in New England. 
Years. Variation at Boston. Falmouth. Penobscot. 
1673 11° 15/ 12° 00 12° 08 
1671S. cde AE GD 11 45 11 53 
1689 10 30: 11 15 11.23" 
1700 10- OObs. 10 45 10 53 
1705 9 46 10 31 10 39 
1710 9 32 10 17 10 25 
1715 9 18 16.22 10 li 
1720 9 5 9 50 9 58 
1725 8 51 9 36 g 44 
1730 8 37 9. 22 9: 30 
1735 8 23 9 8 9.16 : 
1742 8 OObs. 8 45 8 53 
