No. 7.| HORIZONTAL INTENSITY. 73 
in 1895, October 17th, 
December 12th, 
» 1896, January 28th, 
March 19th, 
June 18th. 
If to these are added the observation-days after the return of the expe- 
dition — March 2nd, 1897, in Hamburg, and April 17th and 19th, 1897, in 
Wilhelmshaven — we have 10, what I will call normal, days on which 
determinations of the horizontal intensity have been made with the apparatus 
mounted in the same way, under comparatively quiet magnetic conditions, in 
temperatures varying from — 28° C. on the 28th January, 1896, to + 11°.6 C. 
on the 17th April, 1897. 
THE FINAL VALUES OF THE TEMPERATURE-COEFFICIENT. 
In order to study the temperature-coefficient more carefully, I calculated 
uw from the observations on the 10 normal days, by formula (6), both with 
the value «@ = 0°000307 (Hbg.) found in Hamburg in 1895, and with the 
mean value, «@ = 0°000514 (Ex), found in the above-described manner by 
the observations during the expedition. The result was as follows: 
P.V, 
a = 0:000307 | « = 0:000514 | ¢ + ¢' 
(Hbg.) (Ex.) 2 
Dees 0:076470 0:076033 
May %4 : 0°076045 0:075932 
Oct. 10 0°11637 0711599 0:076140 0:075892 
Dec. 12 0076347 0:075987 
Jan. 28 0°076463 0:076017 
March 19 0°11637 0°11604 0076170 0:075952 
June 18 3 0°11587 0°11596 
March 2 5 0711573 0°11588 : 0:075843 0075945 
April 17 0711617 0°11645 0:076082 0°076264 
— 18 0711618 0°11644 0°075932 0:076098 
If the 4 series of values of w in the table are plotted graphically as a 
t +t 
2 
function of , 4 fairly umform curves are produced, which distinctly 
10 
