THE EARLIEST ISOCLINICS AND OBSERVATIONS 
OF MAGNETIC FORCE. 
BY 
Louis Agricola Bauer. 
[Read before the Society November 10,* 1894.] 
It may interest the Philosophical Society to know that I 
have temporarily removed from Washington in order to 
pursue the study of terrestrial magnetism in European 
libraries. One of the interesting finds growing out of 
these studies is that of a rare book by William Whiston,f in 
the Royal Library at Berlin, containing important matter 
hitherto wholly overlooked. J 
* This paper was completed August 4, 1894, in Germany, and sent to 
Professor Cleveland Abbe, in Washington, D. C., who received it October 
24, and read it before the Philosophical Society November 10, 1894. 
fThe book bears the following title: “The Longitude and Latitude 
found by the Inclinatory or Dipping needle; wherein the Laws of Mag¬ 
netism are also discover’d. To which is prefixed An Historical Preface; 
and to whioh is subjoin’d Mr. Robert Norman’s New Attractive, or Ac¬ 
count of the first Invention of the Dipping needle. By Will. Whiston, 
M. A., some time Professor of the Mathematicks in the University of Cam¬ 
bridge. London, 1721. 8vo, xxviii, 115; iv, 43 pp.; 2 maps and 3 cuts.” 
fThis paper has been in preparation for some time. Whiston’s work 
first became known to me in the winter of 1892-1893. Early in 1894 I 
called the attention of Professor Hellmann and Dr. Eschenhagen to it. 
Since then Dr. W. Felgentraeger, assistant in the Magnetic Observatory 
at Gottingen, has come across the same work and embodied the results 
of his careful researches in an article entitled “ Die Isoklinen Karte von 
Whiston,” published in Nachrichten Kgl. Gesell. d. Wiss. zu Gottingen, 
1894, No. 2, pp. 129-140. As Dr. Felgentraeger’s article does not exhaust 
the contents of the work, I have thought it well to complete this paper 
and at the same time so modify it as to include a discussion of his inter¬ 
esting contribution. 
52-Bull. Phil. Soc., Wash., Vol. 12. 
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