Mr. F. Field on the Silicates of Copper from Chile. 361 



terrestrial surface, as the supposition of a tangential force ade- 

 quate to the elevation required for experiments on free fall close 

 to the earth's surface would prove inadmissible in the present 

 case. At all events, observations on such fugitive phenomena 

 require an uncommon amount of manifold circumspection. 



Professor Laurence Smith concludes his above highly import- 

 ant memoir with the following propositions : — 



1st. " The luminous phenomena attending the appearance of 

 meteorites are not caused by incandescence, but rather by elec- 

 tricity, or some other agent. 



2nd. " The sound comes not from the explosion of any solid 

 body, but rather from concussion caused by its rapid movement 

 through the atmosphere, partly also from electric discharge. 



3rd. " Meteoric showers owe not their existence to fragments 

 caused by the rupture of a single solid body, but to the division 

 of smaller aerolites entering the atmosphere in groups. 



4th. " The black crust is not of atmospheric origin, but is 

 already formed in cosmical space, before the meteorites enter our 

 atmosphere." 



I think (says M. Haidinger) I have now given some expla- 

 nation applicable to each of these four propositions ; some in 

 the same sense (2nd and 3rd), the others (1st and 4th) in a 

 somewhat different sense, without actually excluding mutual 

 compromises. At all events, I would recommend the utmost 

 accuracy in the observations of future meteoric falls, as well as 

 in all investigations concerning those already known. 

 [To be continued.] 



XLIV. On the Silicates of Copper from Chile. 

 By Frederick Field, F.R.S.E., M.R.I.A.* 



ALTHOUGH I believe that crystallized silicate of copper has 

 not yet been found in Chile, several varieties of this mineral 

 exist in very large quantities, generally in amorphous masses, 

 with various shades of colour, some of which are of considerable 

 beauty. These silicates, owing to the great difference in their 

 composition and to the entire absence of crystallization, have 

 not excited the same amount of interest which has been attached 

 to other species, — mineralogists supposing that they are not true 

 minerals, but simply consist of oxide of copper in combination 

 with silica in greater or less proportion, the varieties containing 

 the most oxide being comparatively soft and friable, and the 

 poorer kinds, having but little metal, being exceedingly hard and 

 brittle, resembling in many respects masses of partially fused 



* Communicated by the Author. 

 Phil. Mag. S. 4. Vol. 22. No. 148. Nov. 1 861. 2 B 



