In taxing the property within the State of a company operating in two or more States the not unusual practice has been to levy the tax on the capital stock of the company, taking as the basis of assessment such proportion of its capital stock as the amount of its business within the State bears to the entire business done; and in railroads, telegraph and telephone companies, determining this proportion by the proportion of the total mileage of track or wires lying within the State. This, for example, was the method employed in the leading case of Pullman's Palace Car Co. v. Pennsylvania,39 decided in 1891. This also was the method employed in Delaware, L. & W. R. Co. v. Pennsylvania,40 in which it will be remembered it was held that in appraising the capital stock, tangible property located in other States might not be included.