40 VALUATION, DEPRECIATION AND THE RATE-BASE 
struction. The actual cost, intelligent direction and super- 
vision being assumed, is generally a better guide to the cost of 
accomplishing a result, than the estimate of the expert who, no 
matter how much he knows about present cost, must make 
certain assumptions relating to the past or the future which will 
always brand his conclusions as approximations, even though 
the approximations are in some cases to be accepted as being 
quite as dependable and as acceptable as though they were of 
absolute accuracy. 
It is not proposed to introduce into this volume sample sheets 
enumerating all the various items that may be encountered in 
valuing the various classes of public utilities and industrial 
establishments. The blanks in use for these purposes are ob- 
tainable, at least for the utilities, from any of the public service 
commissions and will be found an excellent guide in listing and 
appraising the physical elements of value. 
The Relation of Present Worth to the Cost of Replacement. — 
After the cost of reproduction has been determined the time 
must be estimated during which — everything considered — 
the article to be valued may reasonably be assumed to continue 
in service. With this time and the probable life new of articles 
of the same class it will, as elsewhere explained, be possible to 
estimate the relation which the present worth of the article 
bears to the cost of replacing it at the time it will probably be 
discarded. If now the cost of reproduction be so modified that 
it will represent the cost of replacing the article at the end of its 
period of usefulness and the present worth or condition factor is 
applied to this cost of replacement the result will be the present 
worth. 
When the property to be valued includes land, rights-of-way 
or water-rights, regard should be had to the principles dis- 
cussed in the chapters on the “ Valuation of Land in Eminent 
Domain Proceedings ” and the “ Value of a Water-Right and of 
Reservoir Lands.” 
Extent of Detail Required. — It has become a common prac- 
tice in valuing property for rate-fixing purposes to approximate