Editorial Covnmetii. 195. 
though agreeing in chemical composition present three distinct 
mineralogical types due to the different conditions of the glassy 
matrix. In the first devitrification has proceeded so far that the 
matrix is a stony dull reddish-gray mass crowded with micro- 
lites. In the second the matrix consists of black pitchstone and 
in the third it is an almost perfect amber-brown glass, or 
obsidian. The last of these on treatment before the blowpipe 
melts and swells up, evidently containing some volatile ingredi-^ 
ent, the presence of which has changed most of the obsidian 
into pumice in the field. Prof. Judd next discusses the effect of 
the presence of water in lowering the fusing point of rocks and 
quotes from the late F. Guthrie a table showing how the fusing 
point of nitre was reduced from 320° C. to 97° C. by the addition 
of about 40 per cent of water. A legitimate inference from 
this experiment seems to be that aqeuous and igneous fusion 
merge into one another so that no line can be drawn between 
them. 
Prof. Judd concludes with the remark that if to a mass of 
nitre lying in the crust of the earth at a temperature of 290° C. 
water should find access, its fusion would certainly follow, and 
that the same result might be looked for in the case of a mass 
of mixed silicates without any rise of temperature. 
PREGLACIAL MAN. 
The controversy over the so called preglacial man between 
Dr. Hicks on the one side and Prof. Hughes on the other, which 
has been going on for some months, is continued in the same 
number. For the clear comprehension of the argument Dr.. 
Hicks should define exactly what he means by the term pre- 
glacial? It may imply "altogether anterior to the ice-age," 
"anterior to the last ice-age," or "anterior to the last stage of the 
last ice-age," and it is impossible to form an opinion from 
the published evidence, without knowing in which sense the 
term is used. Prof. Hughes appears to be unnecessarily scep- 
tical on the subject of preglacial man (using the term in the 
second of the senses given above) or interglacial man as he 
should be called. There is little doubt that we shall soon be 
justified in recognizing such a stage in human history as a reality. 
