75 
of Edinburgh, Session 1866-67. 
into detached islands often miles apart ; and that from the fact of 
so many trap-dyes reaching the surface, even at a distance of more 
than 200 miles from the main mass of volcanic rock, the general 
superficies of the country must have undergone a very extensive 
amount of denudation since the Miocene period. These changes 
point to the passing of an enormous lapse of time, and help to 
teach us that, though in a geological sense the Miocene ages be- 
longed to a recent part of the earth’s history, they are yet separated 
from our own period by an interval too vast to be realised by the 
mind. 
2. Note on the Action of Ammonia on Dicloracetone. By 
Dr A. Crum Brown. 
For some time I have been engaged in an attempt to replace 
the chlorine in monochloracetone and dichloracetone by other 
radicals, and with this object have acted upon them by means of 
cyanide of potassium, acetate of soda, and aqueous and alcoholic 
ammonia. In all of these cases the chlorine was removed as 
chloride of the alkaline metal or ammonium, and brown, tarry sub- 
stances were produced, which resisted all attempts at purification. 
By the action of dry ammonia gas, however, I have obtained some- 
what better results. 
When anhydrous dichloracetone, kept cold by means of a freez- 
ing mixture, is saturated with dry ammonia, white acicular crystals 
are gradually deposited, and these increase in quantity until the 
whole is converted into a white solid mass. If the substances have 
been kept below 0° C., nothing can be seen but these crystals. I 
have not yet been able to analyse them, on account of the great 
rapidity with which they decompose at higher temperature^. If 
the vessel in which they have been deposited be removed from the 
freezing mixture and exposed to the temperature of the room (in 
one case, not above 10° C.), they quickly disappear, and we obtain 
a yellowish liquid, and a copious crystallisation of chloride of 
ammonium. The liquid contains some unchanged dichloracetone, 
and a viscous substance which has a peculiar odour, resembling 
that of acetamide. This substance appears to be colourless when 
