No. 32.] 9 
This delay in the engraving is the true cause of the delay in the pub- 
lication of the 2d volume, which would have been ready one year since 
had there been any prospect of the engraving being soon finished. 
Seeing no immediate necessity of finishing the letter press of the 
volume, and not wishing to do so while I could still make valuable 
additions, I commenced in the autumn of 1849 a revision of the 
corals of the Niagara Group and of the Lower Helderberg limestones, 
(the latter for the 3d volume,) which occupied much of the winter. 
By these examinations I have been able to add some forty species to 
those previously known to me in the Niagara Group, and to estab- 
lish several new genera of importance in the study and classificatiou 
of Palaeozoic corals. 
It can be readily seen that if the law of 1847 was based upon esti- 
mates of the time required to engrave 250 plates, giving me two 
years to collect and arrange materials, and superintend the drawings 
and engravings, the result has fallen far short of the anticipation j for 
in three and a half years, the number of plates executed in lithogra- 
phy and steel engraving has scarcely exceeded sixty. 
The actual state of the present volume is as follows : 
The letter press, containing descriptiorts of 341 species of fossils 
is finished. 
Fifty-eight plates are completed and the number delivered at the 
geological rooms. 
Seven plates more are printed or in progress of printing, and will be 
ready in a short time. 
Twenty plates are in an unfinished state. 
Sixteen plates are not yet commenced. 
This state of the engraving renders it impossible to say definitely 
when the present volume will be published. It can scarcely be less 
than one year from this time; and if no more rapid progress is made 
in the engraving, it will be more than two years before it can be 
published. 
I have the honoi; to be 
Very respectfully, 
Your obedient servant, 
JAMES HALL. 
{Senate, No. 32.] 2 
