SCIENTIFIC SUMMARY. 
369 
axes, with an angle of about 90°. Ouvarovite is regarded as made up of 
twelve pyramids, having the faces of the crystal as their base, and their 
vertices at the centre. The dodecahedrons of aplome and topazolite are 
explained as formed of forty-eight simple crystals. Further than this, M. 
Bertrand found it possible to separate the dodecahedrons mechanically into 
these forty-eight individuals, each one of which is truly biaxial ; the fracture- 
surfaces are smooth and make angles of G0° with the rhombic faces, when 
the plane of separation obtained is parallel to the side of the rhomb, and of 
90° when it is parallel to one of the diagonals. The former fractures are 
obtained more readily than the second, and it is concluded from this that 
the union of the four crystals which form together the same rhombic face 
is more intimate than that of the twelve complex rhombohedral pyramids 
among themselves. That this is the true explanation of these facts may 
perhaps be questioned. — ( Amer . Jour, of Sci., August, 1881.) 
PHYSICS. 
The supposed Heating of Ice. — Dr. A. Wiillner has repeated, by means of 
a modified form of apparatus, some of the experiments described by Mr. 
Carnelley (see Top. Sci. Tevieio for April, 1881). He finds that so long as 
the bulb of the thermometer is completely surrounded by dry ice, its temperature 
does not reach 0° C. If the thermometer rises higher, either the bulb is 
no longer quite covered with ice, or it is surrounded by water together with a 
thicker layer of ice. In other respects the course of the experiment was ex- 
actly as described by Mr. Carnelley. When the bulb becomes partially bare 
of ice, the thermometer will rise even to 50° before the ice becomes detached, 
and rapid heating would probably cause it to rise considerably higher. The 
detached ice, when it comes in contact with the hot glass, dances about like 
Leidenfrost’s drops. 
In order that fusion may not take place, the ice must not be too thick, 
but how thick was not determined. In one experiment the bulb was sur- 
rounded by a coating of ice from 1 to 1*5 centimetre thick, and strongly 
heated by the flame of a Bunsen’s burner ; the temperature rose quickly to 
0°, when fusion commenced, not on the surface, but in the centre of the ice, 
and in such a way that the icater teas forced out through the surface in small 
drops, like blisters, and these, on the removal of the lamp, instantly froze. 
By heating again and again, the same phenomenon was repeated several 
times. 
In a quantitative experiment, 75 grammes of ice were kept under low 
pressure and exposed to the temperature of steam from boiling water for 
five hours ; no fusion occurred, and 42 grammes of ice were volatilized into 
the condenser. — Ann. Cliim. Fhys. xiii. ; Journ. Chem. Soc. No. 226. 
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