5^4 Mechanical Philosophy. 



great use to navigators, and contributed not a lit-- 

 t-Ie toward reducing the principles of this variation^ 

 to something Hke an intelligible form. The next 

 attempt of the same kind, worthy of notice, was 

 t-hat of EuLER. This philosopher, equally re-^ 

 markabJe for the extent of his learning, and the- 

 vigour and comprehensiveness of his mind, vmder- 

 took, about the middle of the century, to account 

 for the magnetic irregularities, and to ascertain^ 

 the position of the needle in every part of the 

 earth. He executed his task with singular inge- 

 nuity and perseverance ; and with a plausible ap- 

 pearance of success. But his theory, and the 

 whole structure founded upon it, were soon found 

 liable to such objections, that they were considered 

 of little value, excepting so far as they might fur- 

 nish a guide in the further prosecution of the in- 

 quiry. Since the time of Euler, many others have 

 exerted their genius in the same investigation }^ 

 but without producing, more certainty or satisfac- 

 tion. Among the latest explorers of this dark but 

 important subject, MY. Churchman, a respectable 

 citizen of our own country, deserves to be honour- 

 ably mentioned. He has, in his own opinion,, 

 made valuable improvements on the theories of 

 Halley and of Euler; corrected various errors^ 

 into which those great philosophers fell; and 

 given an hypothesis which bids fair to be of more 

 practical utility than theirs to the nautical adven- 

 turer. How soon this hypothesis may be brought 

 to the test of a complete course of experiments ; or 

 how it may bear this test, when subjected to it, are 

 questions yet to be solved. In the m^ean time, the 

 ingenuity, zeal and perseverance, evinced in Mr, 

 Churchman's late publications on this subject, de- 

 serve the attention, the thanks, and the encourage- 

 ment of the philosophic world.' 



4^ See Churchman's Magnetic Atlas j 4to. 3d edition j iSoa 



