214 T. S. Hunt on the Chemical and Mineralogical 
alcohol produces alarming symptoms of poisoning in one person, 
while another swallows two hundred drops of a similar solution 
with no other ill effects than a slightly “muddled” feeling in: 
the head. I have experienced unpleasant feelings from tasting 
exceedingly minute quantities of pure nitroglycerine, such as 
headache, buzzing in the ears, with a feeling of nervousness and 
depression, although the action of the drug does not seem to be 
nearly so powerful or so rapid as when it is given in the form 
of alcoholic solution. Pure nitroglycerine is volatile at ordinary 
temperatures-—a fact which was accidentally discovered in draw- 
ing off with a mouth pipette some nitroglycerine which had just 
been washed with water. Headache and the usual symptoms 
immediately set in, though not a particle of the liquid touched 
my mouth or tongue. 
The following experiment, which shows that some constitu- 
tions are susceptible to the action of one-fortieth of a drop of 
glonoine, was made with a solution of nitroglycerine containing 
two and one-half drops of the pure substance to ninety-seven 
and one-half of alcohol. The solution was dropped upon sugar, 
and the sugar allowed to dissolve on the tongue. 
general health being good, and my pulse being seventy- 
nine, about two and one-half hours after a full meal, I took one 
drop of the solution. In two minutes my pulse was ninety-four, 
with dull, throbbing headache; in five minutes the pulse was 
one hundred, the headache changing from the back to the front 
of the head; in ten minutes the pulse was down to eighty-eight, 
i n minutes back to its normal rate, seventy-nIné, 
although the headache did not wholly pass off for fifteen min 
utes more. It will be noticed that a quantity of the solation 
was taken, equal to only one-fortieth of a drop of pure m 
glycerine. 
Walpole, Mass., July, 1863. 
ArT. XX.—On the Chemical and Mineralogical Relations of Meta- 
morphic Rocks; by T. Srerry Hunt, F.RS., of the Geolo 
ical Survey of Canada.’ 
{Read before the Geological Society of Dublin, March 12, 1863.] 
AT a time not very remote in the history of geology, when all 
crystalline stratified rocks were included under the common 
designation of primitive, and were supposed to belong to a p& 
riod anterior to the fossiliferous formations, the lithologist cot 
fined his descriptions to the various species of rocks, without 
reference to their stratigraphical or geological distribution. Bub 
7 From the Dublin Quarterly Journal of Science, for 1863. 
