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EXPLANATION OF TABLE 30 
THE PROBABLE USEFUL LIFE OF VARIOUS ARTICLES OF THE CHARACTER 
Most FREQUENTLY ENCOUNTERED IN PusLic UTILITY VALUATIONS 
The probable life of any article does not depend merely upon 
its wearing qualities when in service, but upon a number of 
other factors as elsewhere explained. Its useful life under aver- 
age conditions is determinable with a greater or less degree of 
approximation from a study of all available experience. 
Without entering upon a full discussion of the basic available 
data, there is here presented a table in which the probable use- 
ful term of life for many articles, appliances, machinery and 
other things likely to be connected with industrial establish- 
ments or with public utilities is noted, due credit being given, 
so far as this is practicable, for the source of information in 
each case. 
Under ordinary conditions and particularly when used in 
connection with the Unlimited Life Method of procedure, the 
life terms here presented are given without any deduction due 
to failure caused by fortuitous events or by inadequacy and 
obsolescence. 
It is to be noted that in some of the sources from which infor- 
mation presented in this table was drawn, the depreciation was 
expressed in percentage by the Straight Line Method. This 
percentage has been translated into years of probable life. 
Summary of Authorities Quoted in Table 30 and Reference to Publication 
Alvord. John W. Alvord in Proceedings American Water Works 
Association, 1903. 
Arbitrators. Board of Arbitration in street lighting controversy at 
Atlanta, Georgia, 1899. 
Arnold. Bion J. Arnold. Coney Island and Brooklyn figures 
adopted by Public Service Commission of New York. 
Four Chicago appraisals quoted by H. A. Foster. 
Bryan. Wm. H. Bryan. “The Appraisal and Depreciation of 
Water Works.” Journal of Association of Engineer- 
ing Societies, Dec., 1907. 
Burdick. Chas. B. Burdick. Appraisal of Mt. Vernon Water Works, 
Illinois, 1906. 
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