368 M. Ampere's Letter to M. Gerhard i on 



Silica -• . . 61-88 



Magnesia 25'83 



Protoxide of iron 9'12 



Oxide of manganese 9*31 



Oxide of chrome 0-33 



Loss by ignition 0'4'5 



106-92— [?] 

 This mineral consequently contains for three equivalents of 

 silica only one of magnesia, and is therefore to be considered 

 as a trisilicate of magnesia ; while the mineral of the olivine 

 kind, from the Siberian and South American masses, as well 

 as the olivine from the basalts, and chrysolite, are merely a sim- 

 ple silicate of magnesia. Whether, moreover, the oxide of 

 chrome that occurs in it really belongs to its composition, or 

 is only accidentally contained in it as an alloy of chrome and 

 iron, cannot yet be decided by these experiments. 



The discovery of this properly olivinic mineral in the me- 

 teoric iron at Gotha not only affords a proof of the difference 

 of this iron from that of Pallas, but is certainly important also in 

 regard to the knowledge of meteoric stones particularly ; be- 

 cause, according to the silica and magnesia which is found in 

 it, it is not improbable that this very kind of oUvine forms pre- 

 eminently the basis of meteorites. 



]^ote. — To the concluding remark of Professor Stromeyer 

 may be added a memorandum of Humboldt on a remarkable 

 aerolite, a notice very interesting in respect to the science of 

 meteoric stones, but still indeed very incomplete. 



At the session of the Pharmaceutic Society at Paris, on the 

 16th May, Baron Humboldt announced that there had been 

 found an aerolite which is really a volcanic production, be- 

 cause it consists of crystals of augite. It remains still doubt- 

 ful whether it was ejected from a lunar volcano. 



I 



LIX. A Letter from M. Ampere to M. Gerhardi on va- 

 rious Electro-dynamic Phccnomena.* 



BEG to return you many thanks for the copy of your ob- 

 servations upon the work of the Chev. L. Nobili which 

 you were kind enough to send me. 



Your answers to several objections contained in that work 

 ao-ainst some parts of my theory of electro-dynamic phaeno- 

 mena appear to me in general very just, and are indeed in my 

 opinion quite satisfactory. They had for the most part struck 



• From tlie Annates de Ch'mie, torn. xxix. p. 373. 



me 



