300 Variation and Dip of the Magnetic Needle. 
gable observer, that, with clock-like regularity, at the expiration 
of every five years, returns to measure the magnetic variation ; 
and how does his zeal reprove the sluggishness of the scientific 
institutions in our country, at many of which the variation of the 
needle has not been even once observed? (5.) The table does 
not purport to be a@ table of observations, but to be “ agreeable to 
the actual observations distinguished by Obs.” The numbers 
marked Obs. were then observed, and the others were computed 
from them, so that six observations were the foundation of the 
whole table. The matter appears to me so plain, that it seems 
useless to argue the question further. The table which is given 
in volume sixteenth of this Journal, has copied the errors of 
Ames’s almanac, and thus, by introducing a little irregularity into 
the numbers, has given them more the air of actual observations. 
The table is still further disguised, by omitting the Obs. which 
marks certain numbers in the original table. If now I have sue- 
ceeded in showing that this “interesting document,” as Mr. De 
Witt terms it, contains but six actual observations, I shall consider 
that I have effected no small object ; for it certainly is a fact not 
very creditable to American science, that a table which Prof. Win- 
throp, nearly three quarters of a century ago, computed for his 
own amusement, should now be referred to as composed of genu- 
ine observations. I have taken the more pains to expose this 
imposition, (for imposition I think it may be called, although @ 
perfectly honest one on the part of Prof. Winthrop, ) because it is 
necessary to be particularly on our guard against confounding cal- 
culations with observations, and because in the progress of my 
investigations, I have met with other tables similar to the prece- 
ding one of Prof. Winthrop. 
I have now mentioned all the new magnetic observations which 
I have been able to collect, and have also stated where other pub- 
lished observations are recorded. The results of all these are 
embraced in the following general table : 
