REPORT ON CHEMISTRY. 
489 
From an inspection of this Table a general idea maybe formed 
of the present state of our knowledge in regard to compounds 
of the first order. Where large gaps occur, the difficulty of the 
investigation, or the rarity of the substances to be combined, 
have presented obstacles which it will still take much time and 
labour to overcome. 
The great strength of chemical research has been expended 
in the formation and analysis of the salts. With a vast num¬ 
ber of these compounds we are already acquainted. Two thou¬ 
sand or more have been already either described or indicated; 
and yet in this more complex branch there are still gaps, wider 
and more frequent than appear in the list above given. We 
are in fact only beginning to see how wide the field is which 
the science of chemistry has yet to explore. 
It was my intention to have inserted here a series of general 
formulae expressive of the composition of the several classes of 
salts, but the limits assigned to this Report make it necessary 
to exclude them. 
In the following Table, ? denotes that certain phaenomena 
appear to indicate the existence of such a compound, but that 
nothing certain has yet been made out. 
“one?” denotes that w T e are acquainted with one such com¬ 
pound, but that its composition is unknown. 
? after a formula, as 2 So + O, ? denotes that such a com¬ 
pound has actually been formed or is supposed to exist, but 
that the composition assigned to it requires confirmation. 
