6Q AMERICAN ASSOCIATION FOR THE ADVANCEMENT OE CH(I. 



ies of each comet by independent observers three to four. Since it has been ab- 

 olished the discoveries of comets have not averaged over three per annum, and the 

 independent simultaneous discoveries of the same comet have become exceed- 

 ingly rare. 



THE UNITED STATES COAST SURVEY. 



The progress of this magnificent work has furnished, as usual, many valuable 

 results in Science since the preceding meeting of the Association ; the following 

 abstracts of the Papers read will shew how great credit is due both to the energy 

 and skill of the conductors of this undertaking, and to the wise liberality of the 

 Government which supports it. 



" The Distribution of Terrestrial Magnetism in the United States," by Prof. 

 Bache and J. D. Hilgard. 



The magnetic observations made in connection with the Survey were scattered, 

 at 1G0 different stations, along the entire sea coast, and the data were reduced to 

 the common period of the year 1850. The line of no' variation, or that passing 

 through all the places where the magnetic needle points to the true north, inter- 

 sects the coast near Ocracoke, between Cape Hatteras and Cape Fear, in a N.N.W. 

 direction, curving gradually to the North, and passing through the middle of 

 Lake Erie. 



To the north and east of this line the declination (or variation of the compass) 

 is to the west of north, being 6° near New York, 10 c near Boston, and 16° in the 

 eastern part of Maine. To the south and west of the line of no variation it is 

 east of north, being 8° east along a line running directly south a little to the west 

 of St. Louis and New Orleans, 18° near San Diego, and 21° near Cape Flattery 

 on the western coast. The dip of the needle varies from 75° in the North eastern 

 States to 60° along the northern shore of the Gulf of Mexico, and the horizontal 

 force from 3.5 to 6.0 in the same regions, 



SUPPLEMENT TO THE PAPER PUBLISHED IN THE PROVIDENCE PROCEEDINGS, ON THE 

 SECULAR VARIATION IN MAGNETIC DECLINATION IN THE ATLANTIC AND GULF COAST 

 OF THE UNITED STATES, FROM OBSERVATIONS IN THE SEVENTEENTH, EIGHTEENTH 

 AND NINETEENTH CENTURIES, UNDER PERMISSION OF THE SUPERINTENDENT. BY 

 CHAS. A. SCHOTT. 



In a paper communicated to the Association at the Providence meeting the 

 secular change of the magnetic declination was investigated by Mr. Schott. In 

 the course of last summer he made some additional observations by direction of 

 the Superintendent of the Coast Survey, and in the paper now presented the results 

 are combined with those previously obtained. The former deductions have gain- ■ 

 ed considerably in accuracy, and have received important additions. The number 

 of stations is increased from ten to thirteen. The recent observations appear to 

 show a slight diminution in the rate of increase of westerly declination, leading 

 to the supposition that the inflexion in the curve representing the secular varia- 

 tion corresponds to about 1850. All the observations concur in placing the 

 minimum about 1800. The present rate of increase of westerly declination is 

 about five minutes annually along the Atlantic coast. 



DISCUSSION OF THE SECULAR VARIATION OP MAGNETIC INCLINATION IN THE NORTH- 

 EASTERN STATES. COMMUNICATED, UNDER PERMISSION OF THE SUPERINTENDENT AND 

 AUTHORITY OF THE TREASURY DEPARTMENT, EY CHARLES A. SCHOTT. 



The results are confined to the limits of 38 deg. and 44 deg. of North latitude, 

 th§ro being too few observations in the southern part of the United States to permit 



