30 PICTURE-WRITING OF THE AMERICAN INDIANS. 
the printed or manuscript works of others. Quotation is still more 
requisite when there is disagreement with the authorities. 
Thanks for valuable assistance are due and rendered to correspond- 
ents and to officers of the Bureau of Ethnology and of the United 
States Geological Survey, whose names are generally mentioned in 
connection with their several contributions. Acknowledgment is also 
made now and throughout the work to Dr. W. J. Hoffman, who has 
officially assisted in its preparation during several years, by researches 
in the field, in which his familiarity with Indians and his artistic skill 
have been of great value. Similar recognition is due to Mr. De 
Laneey W. Gill, in charge of the art department of the Bureau of 
Ethnology and the U. 8S. Geological Survey, and to Mr. Wells M. 
Sawyer, his assistant, specially detailed on the duty, for their work on 
the illustrations presented. While mentioning the illustrations, it 
may be noted that the omission to furnish the scale on which some of 
them are produced is not from neglect, but because it was impossible to 
ascertain the dimensions of the originals in the few cases where no scale 
or measurement is stated. This omission is most frequently notice- 
able in the illustrations of petroglyphs which have not been procured 
directly by the officers of the Bureau of Ethnology. The rule in that 
Bureau is to copy petroglyphs on the scale of one-sixteenth actual 
size. Most of the other classes of pictographs are presented without 
substantial reduction, and in those cases the scale is of little importance. 
It remains to give special notice to the reader regarding the mode 
adopted to designate the authors and works cited. A decision was 
formed that no footnotes should appear in the work. A difficulty in 
observing that rule arose from the fact that in the repeated citation of - 
published works the text would be cumbered with many words and 
numbers to specify titles, pages and editions. The experiment was 
tried of printing in the text only the most abbreviated mention, gen- 
erally by the author’s name alone, of the several works cited, and 
to present a list of them arranged in alphabetic order with cross 
references and catch titles. This list appears at the end of the work 
with further details and examples of its use. It is not a bibliography 
of the subject of picture-writing, nor even a list of authorities read 
and studied in the preparation of the work, but it is simply a special 
list, prepared for the convenience of readers, of the works and authors 
cited in the text, and gives the page and volume, when there is more 
than one volume in the edition, from which the quotation is taken. 
