C 75 ) 
W. An Account of form Magnedcal Obfer- 
various made in the Months of May, June 
and July, 173 2, in the Atlantick or 
of a Water-Spout, by Mr. Jofeph Harris. 
Communicated by Mr. George Graham, 
T HE Knowledge of the Magnetic al Variation is 
of fuch Confequence to the Mariner, that 
without it he cannot know hisCourfe ; and were the 
Theory thereof once eftabliftied, it might be of great 
ufe for eftimating the Longitude in feveral Parts of 
the World, as has been often and very juftly obferv- 
ed by others. But ’till this be determin’d, we mud: 
rely upon Obfervations. 
I fometime fince took notice of the Imperfeffions 
of the common Azimuth Compafs, and how ill 
adapted that Indrument is for the Purpofe intended, 
I alfo gave the Defcription of a new Inftrument, 
whereby I propofed to remedy the principal ObjeQa- 
ons to the former ; and farther Experience has fuffici- 
ently. confirmed me in what I have faid. But I fhould 
be glad to have it determined by thofe who have con- 
venient Opportunities of making Experiments of this 
kind, ,what would be the propereft Diameter and 
Weight for a Needle and Card, and what ought to 
be their proportional Weights to each other when 
taken feparately : Regard being had tjjat the Fri&ioe 
F. S. 
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