134 
PROFESSOR W. G. ADAMS ON A COMPARISON OF SIMULTANEOUS 
be seen that the instruments of the same type at the different observatories still have 
very different degrees of sensitiveness. 
In some cases the scale-values of the magnetic instruments have not been deter¬ 
mined, especially in the case of vertical force instruments. Hence the number of 
stations to which Gauss’s method is applicable is very limited. 
On June 24th, 1885, a magnetic storm began quite suddenly at 10.32 P.M., Green¬ 
wich mean time, in which there were several well-marked features. 
At 3.48 A.M., on June 25th, there was a sudden and very great disturbance; at 
10.20 A.M., there was another characteristic, but rather small disturbance, and a larger 
disturbance at 12.15 p.m. The storm continued until about 8 A.M., on June 26th. 
The values of certain sudden changes in the magnetic elements and the comparative 
scale-values of the self-recording instruments are given in Table III., except in cases 
where they are too small, or where there are no means of determining them. From this 
table it will be seen that at several European stations the sudden change in the 
horizontal force, at the beginning of the storm, is nearly the same ; also the change in 
the horizontal force at 3.48 a.m., on June 25th, is nearly the same in amount at 
European stations, and at Colaba and Batavia. 
The disturbance at Toronto is very abnormal in all the magnetic elements, and far 
greater than at any other station. 
In Plates 8, and 9, the curves have been carefully traced from the photographic 
records, and set to Greenwich mean time, and grouped so as to bring out prominently 
the common features from widely distant stations. 
