X 
PREFACE. 
but the greater part for the third volume, as well as extensive collections 
in the higher rocks of the New-York series for the succeeding volumes. 
Besides these, I had made large collections of fossils in the same series 
of strata in the west, for the purpose of comparison with the New-York 
species. In this way, as well as in examinations of the rock formations 
in situ over a large part of the Western States for the purpose of de¬ 
termining the parallelism of the formations, I had already made great 
pecuniary sacrifices in carrying on the work. Under these circumstances, 
therefore, and with the new aspect presented by the law of 1850, and 
the action of the Commission relative thereto, I could no longer devote 
myself to its prosecution, and consequently made other arrangements 
for the occupation of my time, which, however, left me still some op¬ 
portunity to continue my investigations in this work. As the contracts 
between the State and the engravers continued in force, the engraving, 
after 1851, was carried on somewhat slowly; my frequent and protracted 
absence rendering it impossible for me to give that personal attention 
to it which a work of this kind so fully demands. In order to prevent its 
entire cessation, I employed a person as an assistant (who afterwards 
became my draughtsman); the lithographer volunteering to contribute 
to pay a portion of the expense of such assistant, that his own work 
might not cease entirely. In this way the work was continued till 1855 ; 
no compensation whatever being paid to the author during this period. 
In the latter part of 1854 and beginning of 1855, the attention of 
the then Secretary of State, lion. E. W. Leavenworth, was called to the 
consideration of this subject by Professor Dewey of Rochester, who had 
taken some pains to procure information in relation to the state and 
progress of the work. Mr. Leavenworth, with his enlightened views and 
the patriotic desire to see a work, which had been begun by a wealthy 
and powerful State, completed in a proper manner, inquired into its 
actual condition, and, finally, when I had decided to abandon it al¬ 
together, procured the passage of a law, giving to himself and the 
Secretary of the Regents of the University the power to make such 
contracts and provide such means as were necessary for carrying it on 
