Chemistry and Physics. 451 
calcite, nevertheless the resulting form possesses a remarkably 
high degree of symmetry, and approximates very closely to 
that which would be produced by a twinning parallel to the 
plane 2-2. The two adjacent crystals are united by the twin- 
ning-plane, and the two diagonally opposite by a plane normal 
to this, but the same law of twinning applies to both cases. 
It can hardly be questioned that-this fact, that by this method 
of grouping the form of the quartz approximates so closely to a 
form which might well exist independently, must be at least a 
partial reason why it is here placed in so remarkable a geomet- 
rical relation with calcite. 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND PHYSICS. 
1, On the Size of Hydrogen Atoms.—ANNAHEIM has described 
asimple lecture experiment in which the coloring power of fuchsin 
and cyanin is made use of to illustrate the extraordinary divisibil- 
ity of matter. To form an idea of the amount of coloring matter 
visible to the naked eye, he weighed out 0°0007 gram fuchsin 
3HCl)—a fragment about half a millimeter in diameter 
—dissolved it in alcohol and diluted the solution to a liter. 1p each 
is 337°5, the maximum weight of a hydrogen atom iS 337-5 
0°00000002 gram, or 0000000000059 gram! The sam 
One milligram dissolved in 
ae 
51, September, 1876. #3 
2. On the Atomic Weight of Selenium.— PETTERSSON and Ex- 
lenium, yzing for this purpose calcium, m um and 
silver selenates, siti ee se fetta Jenate, silver selenite, tt 
selenous oxide, all of the greatest attainable purity Silver selen- 
data for determini ight are obtain 
ng the atomic wel are ¢ 
of seven anal yses, che atomic weight obtained was 79°01. By 
