151 
aurin is C 14 H n (OH) 3 . Already, in our first research, we ob- 
tained results which seem to confirm this view. On heating 
aurin with acetyl chloride," we obtained a colourless crystal- 
line compound, which on analysis gave results nearly agree- 
ing with the composition of triacetyl aurin C 19 H 11 (0C 2 H 3 0) 35 
and on using benzoyl chloride a similar benzoyl-compound 
was obtained. The analytical numbers did not, however, 
sufficiently agree with those required by theory, and there- 
fore we did not publish them ; and, as the purification of these 
compounds was found to be beset with several difficulties, 
we did not then examine them further, because we believed 
the study of red aurin would more readily throw light on 
the subject. We have now prepared them again from pure 
aurin, and hope to be soon able to settle these points. 
“The Origin of some Ores of Copper.” Part II. By 
Charles A. Burghardt, Ph.D., The Owens College. 
A tacamite. 
This interesting and beautiful mineral occurs generally in 
radiating foliated masses, or in bundles of acicular crystals 
which are characterised by a fine vertical striation upon 
their vertical faces. Globular, reniform, and stalactitic 
atacamite is also known. Thus it is safe to infer that in 
a great majority of cases the mineral has been formed in 
some way from a solution of copper salt, and not by igneous 
action. It is also a well known fact that atacamite crusts 
are occasionally found resting upon clefts in the lava of 
some volcanoes, being formed by the action of hydrochloric 
acid gas evolved by the volcano upon copper, or a compound 
of that metal, but these crusts are insignificant in quantity 
and comparatively scarce. In Chili, Bolivia, and the West 
Coast of Africa, very large quantities of atacamite are 
obtained as a commercial product; it therefore becomes 
interesting to the mineralogist to ascertain under what con- 
ditions these formations arose, and in order to do this a 
thorough chemical examination of the mineral itself is 
