428 VALUATION, DEPRECIATION AND THE RATE-BASE 
TABLE 30. THE PROBABLE USEFUL LIFE OF VARIOUS 
ARTICLES (Continued) 
Description. Epoch Residual) Authority. Remarks. 
Years = 
Storage batteries. ............ 10 M.E.R.&L.Co Milwaukee 3¢ Fare Case. 
10 Wis. R. R. Com Milwaukee 3¢ Fare Case. 
12.5 6% P.G.&E. Co. S.F.rate hearings, 1913-14. 
15 5% Wis. R. R. Com. Wisconsin Tel. Co. Case. 
15 Chi. U./T. Co. Chi. Union Trac. Co. Case. 
20 Stone & Webs. Chi. Union Trac. Co. Case. 
20 St. Louis P. S. C. Union Elec. L. &P. Co. Case. 
20 Floy ard Ave. Case, N. Y. City. 
Sub-station equipment. ....... 20 S.J. L.&P. Cor. Cal. R.R. Com. rate hearing. 
Z5 Preece Report Bristol Corp., 1906. 
50 Cal. R. R. Com. Calis. E. C. vs. Napa Val 
E. C. 
Sum ps and wells 
at gas plant... LLL LEE 30 P.G.&E. Co. S.F. rate hearings, 1913-14. 
tar and ammonia. ........ 50 Wis. R. R. Com. Quoted by H. A. Foster. 
Surge tank 
concrete’... . avu d del I 30 S.J. L.& P. Co. Cal. R.R. Com. rate hearing. 
Superheaters..:... vedas 20 P.G.&E. Co. S.F. rate hearings, 1913-14. 
Switchboards. ......coevinnn 12} St. L. P.S. C. Union Elec. L. & P. Co. Case. 
15 Chi. U.!T. Co. Chi. Union Trac. Co. Case. 
16.7 Arnold Coney Isl. & Brooklyn Case. 
20 Stone & Webs. Chi. Union Trac. Co. Case. 
20 M.E.R.&L.Co Milwaukee 3¢ Fare Case. 
20 Floy 3rd Ave. Case, N. Y. City. 
20 P. G.&E. Co. S.F. rate hearings, 1913-14. 
20 Hammond Jour. Inst. Elec. E., 1907. 
15-20 S.J. L. & P. Co. Cal. R. R. Com. rate hearing. 
15-20 Wis. R. R. Com Milwaukee 3¢ Fare Case. 
33.3 Trac. Val. Com. Chi. Con. Trac. Co. Case. 
50 Arnold 4 Chicago Appraisals. 
50 Chi. Trac. Com. Quoted by G. W. Cravens. 
50 Wis. R. R. Com. Quoted by G. W. Cravens. 
telephone, central. ........j 8 20% Chi. Tel. Com. Chicago Telephone Com. 
telephone, central. ....... | 8-10 15% Tel. * Data” Quoted by H. A. Foster. 
telephone, central. ........, 12 20% Wis. R. R. Com. Wisconsin Tel. Co. Case. 
telephone P. B. X......... 8 20% Chi. Tel. Com. Chicago Telephone Com. 
telephone P. B. X........ | 10 10% Tel. * Data” Quoted by H. A. Foster. 
telephone P. B. X......... 10 15% Wis. R. R. Com Wisconsin Tel. Co. Case. 
Systems and plants 
electric light and power.... 17.46 Wis. R. R. Com. Fon du Lac W. Co. Case aver. 
6 plants. 
electric light and power.... 18 | Wis. R. R. Com Madison Gas & E. Co. Case. 
electric light and power.... 20 Mass. G. & E. Mass. Gas & Elec. Com. 
Com. 
electric light and power.... 20-25 Wis. R. R. Com. Jefferson Mun. E. L. & w. 
plant. 
electric light and power.... 22.0 P. G. & E. Co. S. F. rate hearing, 1913-14. 
electric railway............ 18.02 Wis. R. R. Com Fon du Lac W. Co. Caseaver. 
7 plants. 
electric railway............ 18.6 Wis. R. R. Com Milwaukee 3¢ Fare Case.