TRIP TO THE YELLOW STONE. 207 
dificulties that stood in the way: with his ex- 
perience, and with his usual energy to help him, 
bending his mind to the task he had thus taken 
up, he at once began to arrange his plans, and 
having decided to bring out the work in a size 
suflicient to give figures of all the animals 
not larger than the raccoon, of their natural 
dimensions; he soon was deeply engaged in 
preparing it. 
He was aided in this arduous task, not only 
by Dr. Bachman, but by his sons, V. G. and 
J. W. Audubon, the former painting the back- 
grounds, drawings of trees, plants, etc, and 
editing the manuscript for the press, and the 
latter procuring and drawing some of the ani- 
mals in Texas, California and elsewhere. 
Audubon was also assisted by hosts of friends, . 
many of whom are named in the introduction 
to the work, including Sir George Simpson, of 
the Hudson’s Bay Company, the Chouteaus, of 
the American Fur Company, etc, etc. This 
work involved the necessity of further journey- 
ings, and among the rest, a trip to the Yellow 
Stone river and the spurs of the Rocky Moun. 
tains, which expedition was made in 1843, and 
was productive, besides its results in respect to 
the history of the quadrupeds, of further dis: 
voveries in ornithology, some twenty new 
epecies of birds having been added by it to the 
