452 Scientifie Intelligence. 
* 
colored bands. This feature I have best seen in the interior « 
in na 
largest cavity is a ragged shallow one two inches long A one 
broad ; and another has half these dimensions, These cavi- 
Ges contain a coating of limonite. The prying action sstendiog 
the oxydizing BP ocess tends to loosen grains as well as open crevi- 
ces; but, if the quartzyte were originally solid, the mechanical 
removal of the ‘separated grains so as to make cavities in its inte- 
rior would be impossible. The cavities may have been produced 
the removal of largish pieces of pyrite, or of both pyrite and 
feldspar, but whether so or not, the facts are insufficient bosianay 
to determine. The presence of feldspar is rendered probable by 
the occurrence of a kaolin-like material in a few otherwise empty 
cavities in the body of the quartzyte. 
Further: the cavities described have generally a lining of minute 
erystals of quartz ; and these crystals coat the limonite, showing 
that the crystals were deposited after ie limonite. The drusy 
quartz also penetrates to such an extent the limonite-colored 
bands, that it is probable that they were formed also during the 
making of the limonite, and at the ordinary temperature. 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND PHysICcs. 
nm the Cause of the discrepancy between the observed 
O. 
Bastrom otive force of a Battery and that calculated from 
thermochemicat data.—Many voltaic cells have an actual 
these, those containing iron, eee or cobalt in a solution of 
potassium hydrate, for example, show polarization phenomena 
markedly, as Becquerel pointe d ain in 1856. These cells, 
though the positive electrode is unpolarizable, give a current 
which rapidly fi ro. So a cell having an electrode of 
uminum in dilute sulphuric acid aoa one copper in sulphate 
of copper solution, gives an electromotive force of only 0°62 volt 
instead = as required b sca and a cell bawing 
Cuaprron has accordingly made a series of experiments upon 
