445 
1879*] Proceedings of Societies, 
1. That the diurnal ranges of the magnetic elements of de- 
clination and horizontal force are subjedt to a periodical 
variation, the duration of which is equal to that of the 
known eleven-year sun-spot period. 
2. That the epochs of minimum and maximum of magnetic 
and sun-spot effedt are nearly coincident ; the magnetic 
epochs, on the whole, occurring somewhat later than the 
corresponding sun-spot epochs. The variations of dura- 
tion of different periods appear to be similar for both 
phenomena. 
3. That the occasional more sudden outbursts of magnetic and 
sun-spot energy, extending sometimes over periods of 
several months, appear to occur nearly simultaneously 
and progress collaterally. 
4. That it seems probable that the annual inequalities of mag- 
netic diurnal range are subjedt also to periodical variation, 
being increased at the time of a sun-spot maximum, when 
the mean diurnal range is increased, and diminished at 
the time of a sun-spot minimum, when the mean diurnal 
range is diminished. 
Conclusions Nos. 1, 2, and 3 appear to be sufficiently certain, but 
the evidence in favour of No. 4 is not so decisive. 
“ On the Results of the Magnetical Observations made by the 
Officers of the Ardtic Expedition, 1875-76,” by Staff-Commander 
E. W. Creak, R.N., attached to the Admiralty Compass Depart- 
ment. This narrative and results form the sequel to the 
“ Memorandum on Terrestrial Magnetism,” prepared by Prof. 
J. C. Adams, M.A., F.R.S., and Capt. F. J. Evans, R.N., F.R.S., 
published in the “ Manual and Instructions for the Ardtic Expe- 
dition,” 1875,” suggested by the Ardtic Committee of the Royal 
Society. The Alert and Discovery left Portsmouth on May 29th, 
1875. On September 1st, 1875, the Alert reached her winter 
quarters at Floeberg Beach, lat. 82° 27' N., long. 6i° 22' W. 
The magnetic observatory, constructed entirely of snow, was 
situated at a distance of 200 yards from the ship. It was 
divided into three distindt houses 27 feet apart, and in these the 
horizontal force magnetometer, Barrow’s dip-circle, and the 
differential declination magnetometer were secured to snow 
pedestals. As no stove was used the range of the thermometer 
registered was from — io° to -f-4 0 . The Discovery took up winter 
quarters at Discovery Bay, 53 miles S.W. of the Alert , in lat. 
8i° 44' N., long. 65° 3' W., on August 26th, 1875. The mag- 
netic observatory house was constructed of wood, and stood on 
the shore 197 yards from the ship, and the pedestals formed of 
the ship’s binnacles sunk into the ground were found to be very 
firm. For the differential declination magnetometer an ice house 
was built on the ice-floe 90 yards from the ship, the magnet- 
ometer being frozen on to a pedestal of ice. One of the chief 
subjects of interest in the magnetical results of the observations 
2G2 
