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assistance from those capable of adding to its accu- 
racy ; and too flattering to its author, not to excite 
in him a wish of exculpating himself from any cen- 
sures it may seem to contain against him. Yet these 
two objects would hardly have occasioned my trou- 
bling you with the present letter, had I not thought 
it justice to the public to avow some mistakes into 
which I have fallen, and at the same time to account 
for a longer delay of the remaining volumes than I 
once intended; for both which communications I 
have judged your Review the most proper vehicle. 
The reason assigned in the Preface, for publish- 
ing the work in an incomplete state, is really and 
truly the only one that operated with me at the 
time: it was suggested by my publisher, and had 
the sanction of my most enlightened friends. I 
had then continued my manuscript far into the last 
class among the Mosses and Lichens; and had 
thought of nothing less than postponing that part, 
being determined to finish the work as completely 
as was then in my power. Since the publication, 
however, of the first two volumes, several new mo- 
tives have presented themselves, which oblige me 
to defer the sequel longer than I intended. Ist, I 
wish to see Mr. Dickson’s fourth Fasciculus of 
Cryptogamia, which is on the point of publication : 
2ndly, The Prodromus Lichenographie Suecice of 
Dr. Acharius takes the lead so much in that de- 
partment, it is absolutely essential to my purpose 
to compare specimens with that author; and this 
cannot be done either in the winter season, or in 
the present miserable state of Northern politics. 
