ON EARTH TREMORS. 



149 



I am indebted to Dr. Eschenhagen for copies of the six curves. Two 

 of these (those of the declination and horizontal intensity on April 27) are 

 shown in fifrs. 1 and 2. 



Fig. 1.— Potsdam : Declination, April 27, 1894. 



Wilhelmshaven (Dr. C. Borgen), 53° 31' 52" N., 8" 8' 48" E. The traces 

 on the magnetic curves consist of a slight broadening of the curves. The 

 times read off are those of the beginning of the disturbance in each case. 



April 20, Declination 

 Bifilar 

 Lloyd's Balance 



April 27, Declination 

 Bifilar 

 Lloyd's Balance 



Pare St.Maur (M.Renou and M. Moureaux), 48° 48' 34" N., 2° 29' 38" E. 

 No trace of any disturbance exists on the magnetic curves on April 20. 

 On April 27 two pulsations are perceptible on the declination curve, the 

 first very feeble at 7h. r)4m., the second more marked at 7h. 59m. p.m. 

 The curves of the two components of magnetic force are apparently undis- 

 turbed. Two bars of copper with bililar suspension, orientated N.S. and 



