A complicated spectrum may consist of hundreds or thousands of lines, due to the presence of many different substances in the source of light, and unless great care is taken in assigning the exact position of these lines in the spectrum, confusion and wrong identifications are sure to result.
"A Text-Book of Astronomy"
George C. Comstock
The reader who is curious on the subject, will find in Dr. A. Wright's article a brief account of the various identifications proposed by all these commentators.
"Creation and Its Records"
B.H. Baden-Powell
Even popular definitions serve as rules for identifying and classifying individuals, but the purpose of such identifications and classifications is mainly practical and social, not intellectual.
"How We Think"
John Dewey