March 4, 18b7.J 



SCIENCE. 



217 



of 1.30 to 1 : in the annual variation the disturb- 

 ing force was most active during November and 

 least during September. In the diurnal variation 

 the easterly and the westerly disturbances follow 

 different laws as to frequency and amount. The 

 disturbing force deflecting the north end of the 

 needle towards the (magnetic) east is most active 

 two hours after midnight and least active during 

 the hours 13 to 17 (or afternoon hours). On the 

 other hand, deflections to the west appear most 

 frequent three hours after noon and least about 

 the hours near midnight. Respecting intensity of 

 action, easterly disturbances slightly exceed wester- 

 ly ones. 



The term-day and term-hour observations ex- 

 tend over the interval from July 1, 1883, to Aug. 1, 

 1883. They were made on the 1st and 15th of each 

 month, when the declination magnet was observed 

 every five minutes throughout the twenty-four 

 hours, simultaneously at all stations taking part in 

 the research. Besides these, observations were 

 made every twenty seconds during one selected 

 hour on each of the term-days. The labor be- 

 stowed upon this part of the work was very great, 

 but it is expected that correspondingly valuable 

 results may be deduced by their inter-comparison 

 after all the expeditions shall have published their 

 observations. Not content with these labors, the 

 magnetic observers also recorded the motion of 

 the needle during magnetic storms and in connec- 

 tion with appearances of auroras. 



The usual observations of oscillations and de- 

 flections were made for the determination of the 

 magnetic intensity : the record and computations 

 are given in detail and the results are tabulated 

 and expressed in British, Gaussian, and C. G. S. 

 units, or dynes. For the epoch 1883-84 the hori- 

 zontal component of the magnetic force was 

 found 1.118 British units, or 0.05155 dynes, and it 

 would appear from comparison with the results 

 found by the British exploring expedition, 1875- 

 76, that this intensity did not undergo any per- 

 ceptible change during the interval. The tabular 

 values show extreme variations of about one- 

 fiftieth part of the force. 



Hourly observations of the dip were made be- 

 tween Sept. 35, 1883, and June 1, 1883. These 

 were in a measure differential, and resulted in an 

 average dip of 85° 01'. Combining with the hori- 

 zontal component, the total intensity as observed 

 at Fort Conger becomes 13.870 British units, or 

 0.5934 dynes, for the epoch 1883.8. By compari- 

 son it was found that the dip had been increasing 

 since 1875-76 at an annual rate of 1'.6. 



The dates of auroral displays are next enume- 

 rated, and extracts are given of the character of 

 the more imposing auroras. Then follows a table 



of magnetic results, collected during explorations 

 by different parties, and extracted from Lieutenant 

 Greely's narrative. The paper concludes with a 

 general collection of magnetic results obtained 

 from the expeditions of Kane, 1853-55, of Hayes, 

 1860-61, of Hall, 1871-73, of Nares, 1875-76, and 

 from Lieutenants Crosby and Sebree of the Bear 

 and Thetis in 1884. From these observations it is 

 concluded that for the last twenty-five years, at 

 least, the magnetic west declination has been an- 

 nually decreasing about 6' in the region of the 

 North Water, Smith Strait, and Kane Basin, and 

 that in the region to the north of it, and including 

 the Hall Basin, this decrease was fully 10' per year 

 during the past decade. 



In close connection with the scheme of physical 

 researches undertaken by the International arctic 

 committee, the desirability of a new determination 

 of the American pole of dip does not appear to 

 have been urged. It must be admitted that the 

 region is difficult of approach ; yet the gain to our 

 knowledge of terrestrial magnetism and its secular 

 changes would be very certain if it could be 

 successfully explored. More than half a century 

 has elapsed since Ross made his memorable and 

 bold dash to this point, but science nowadays will 

 demand more, and the whole region in that 

 vicinity would have to be surveyed in order to per- 

 mit the tracing out of isoclinics or the application 

 of a suitable analytical process to bring out the 

 facts of the case, as, in consequence of local de- 

 flections, there may be many points of vertical dip 

 covering or distributed over a considerable area. 



From the time of Hansteen, early in this cen- 

 tury, to the present time, efforts have been made to 

 trace out the supposed motion of the intersection 

 of the so-called magnetic axis with the surface. 

 While some physicists hold it to be fixed in posi- 

 tion, others believe it to have a slow secular mo- 

 tion of limited extent, and still others would give 

 it a rapid motion with a path which will carry it 

 clear round the geographical pole. 



The time has certainly arrived when in this 

 matter facts should take the place of speculation. 

 The writer has the assurance of the willingness of 

 three distinguished American Arctic explorers to 

 undertake this task, only the one thing lacking is 

 the necessary funds to sustain the explorer, say 

 for two years. 



There is surely here a fine field open in which to 

 gain well-merited distinction. C. A. S. 



A NEW departure has been made by the U. S. 

 coast survey by way of experiment, in the publi- 

 cation of a chart on Mercator's projection, extend- 

 ing from New York and embracing Nantucket 

 shoals. 



