40 



This table exhibits a considerable number of gaps, which the pro- 

 gress of science will not be long in filling up. Even now we have 

 established by experiment that bromide of amylene suffers many 

 changes, which are perfectly analogous to those which we have wit- 

 nessed in the acryl series, and even the derivatives of olefiant gas 

 appear to exhibit in many respects an analogous deportment. 



February 14, 1856. 



Dr. W. A. MILLER, V.P., in the Chair. 

 The following communication was read : 



" On Periodical Laws discoverable in the Mean Effects of the 

 larger Magnetic Disturbances." No. III. By Colonel 

 EDWARD SABINE, R.A., D.C.L., Treas. and V.P.R.S. 



(Abstract.) 



In two previous papers bearing the same title as the present 

 (Phil. Trans. 1851, Art. V., and 1852, Art. VIII.), the author 

 showed, from the hourly observations of the magnetic Declination at 

 Toronto and Hobarton, that the magnetic disturbances of large 

 amount, and apparently irregular occurrence, commonly called mag- 

 netic storms, are found, when studied in their mean effects, to be 

 governed by periodical laws of systematic order and regularity, and 

 to exhibit periods whose duration is, respectively, 1, a solar day ; 

 2, a solar year ; and 3, a period of about ten of our solar years, 

 corresponding both in duration and in the epochs of maximum and 

 minimum variation, to the approximately decennial period discovered 

 by Schwabe in the phsenomena of the solar spots. In the present 

 paper the author communicates the results of a similar investigation 

 into the laws of the disturbances of the two other magnetic elements 

 at Toronto, namely, the Inclination and the Total Force, derived from 

 the hourly observations of the horizontal and vertical Forces during 

 the five years from July 1843 to June 1848 ; affording, as he states, 

 a full confirmation of the existence of periodical laws regulating the 

 disturbances of the Inclination and Total Force corresponding to 

 those which he had previously deduced from the disturbances of the 

 other magnetic Element, viz. the Declination. 



