360 
MR. JOHNSTON ON THE CONSTITUTION OF THE RESINS. 
radicals, or hydrates containing the elements of water in a state of direct combination; 
or whether they be not rather formed by the union of two or more compound oxides; 
these are questions the greater number of which we are as yet far from being pre- 
pared to discuss with any chance of arriving at the truth. I waive, therefore, the 
consideration of all these points for the present, in the hope that light will sponta- 
neously break in upon many of them, when in a succeeding part of this research I 
shall study the relations of the resins to the most important chemical reagents. 
One important point may be considered as nearly established by the analyses 
already made, namely, that the constant Qo is characteristic of the irrational formulae 
for this group of natural productions ; and it is interesting to find that in exhibiting 
such a characteristic, it bears a striking resemblance to other groups, not very di- 
stantly allied to it, either in the physical properties they possess, or the natural 
sources from which they are obtained. I refer especially to the fixed and volatile 
oils, in many of the known formulae for which a similar constant is to be traced, 
and in which the number represented by x may be considered as characteristic of a 
more or less extensive natural group. I shall have an opportunity of illustrating 
this observation in a future paper. 
Durham, March 13, 1840. 
