160 
alcoholic extract shows after insolation a marked acid reac- 
tion. It would be interesting to ascertain whether alcoholic 
extracts of other leaves containing much essential oil behave 
in the same manner as Eucalyptus extract. I made the ex- 
periment with leaves from the orange tree, in which, as in 
Eucalyptus leaves, numerous oil cells may be seen under a 
lens, but the alcoholic extract, on being kept for several days 
in the dark, remained unchanged. After insolation it dif- 
fered slightly from an extract of grass made at the same 
time and exposed along with it to sunlight, bands I and 
IV(X remaining visible, while the corresponding bands of the 
grass extract had disappeared. 
“ On the Chemical Composition of the Ink on Letters and 
Documents as Evidence in Legal Cases,” by William 
Thomson, F.KS.E. 
The ideas which I propose to bring before you are not 
entirely new. They are based on the examination of the 
ink on letters and documents as a valuable mode of inves- 
tigation in civil and criminal law cases. 
It frequently happens that circumstantial evidence of a 
very simple character which is often overlooked, might 
occasionally have the effect of conclusively proving the 
innocence or guilt of an accused person, or of pointing in 
some definite direction towards tracing the culprit. In civil 
legal cases the same class of evidence may prove equally 
useful. 
If, for instance, a person be murdered on the highway and 
any weapon or instrument found with which the deed had 
been committed, it is needless to say that such implement 
would be carefully examined for name, mark, or number, or 
in fact any peculiarity by which it may be traced to its for- 
mer owner. Again, recent foot-prints in the snow or in soft 
clay often present sufficient individuality about them to 
make them useful in the detection of crime, and these 
