Miscellaneous Intelligence. 79 



and not changing all the magnetic forces into heat through 

 natural decay, will go far to explain the phenomena of the 

 spasmodic disturbances. 



The aurora. — The atmosphere screens ofi only a part of the 

 components resolved parallel to the earth's axis, so that we have 

 a field of lines of induction which may be again resolved parallel 

 to the axis of the permanent magnetism of the earth. The effect 

 of these conditions is to gather up such lines of force around the 

 poles, and they may produce a system of relations like those seen 

 in the aurora. A test can be applied by measuring whether in 

 inclination the upper parts of the auroral beams are bent more 

 rapidly towards the poles than the theoretic lines of force pro- 

 duced under the laws of the magnetic potential will admit. 



IV. Miscellaneous Scientific Intelligence. 



1. Mexican Meteorites. — Mr. Fletcher of the British Museum 

 has made and published in the Mineralogical Magazine an ex- 

 haustive study of the numerous Mexican meteoric irons. He has 

 collected the original accounts relating to the numerous irons 

 that have been brought from Mexico. The following are his 

 conclusions respecting the dispersion of these iron masses over 

 the several Mexican States : 



"In each of the States of Zacatecas, Oaxaca and Guerrero, only 

 a single mass of meteoric iron has been found, and there is abso- 

 lutely nothing to suggest that they do not represent independent 

 falls. 



"In Sinaloa, likewise, only a single mass has been met with, 

 and its characters have not been determined : a suggestion of a 

 relationship with another group would rest on the slight fact that 

 the site of an extremely large mass is in a straight line with two 

 other sites where large masses are now lying. 



"In San Luis Potosi two localities are recognized, but there 

 is a strong probability that the Charcas mass, which has un- 

 doubtedly been transported to that town from a distance, was 

 brought from the neighbourhood of Catorce : and, even if this 

 was not the case, there is no evidence that the mineralogical 

 characters are such as to render separate falls improbable. 



"In Durango four or five distinct localities are known, but the 

 characters of the only masses which have been examined point 

 unmistakably to the falls of distant masses having been independ- 

 ent of each other. 



"In Mexico there has undoubtedly been a large shower of 

 limited dispersion in the Valley of Toluca : the three remaining 

 masses from Mexico and Morelos have not been examined, and 

 are very small and portable : even if they have not been trans- 

 ported, they may be found on examination to present characters 

 which will differentiate them from the masses of the Toluca 

 shower. 



