“ The prohibition in section 3 (1) of the Interstate Commerce Act of any undue preference of one locality over another always has been treated as intended to prevent the use of rates as a means of promoting the artificial development of one locality to the detriment of another. And what is said about the maintenance of an adequate system of transportation is but a reiteration of provisions embodied in existing laws. ”

“ If they mean no more than that the depressed condition of the industry is to be given such consideration as may be reasonable, considering the nature and cost of the transportation service and the need for maintaining an adequate transportation system, they work no change in the existing law. But, if they mean more, and are intended to require that rates be reduced to some uncertain level below that standard, they give rise to a serious question respecting the constitutional validity of the paragraph of which they are a part. ”

“ The words stressed are, 'at the lowest possible lawful rates compatible with the maintenance of adequate transportation service.'
Considering the connection in which these words are brought into the sentence, we think they fall much short of supporting the construction adopted by the Commission. They are more in the nature of a hopeful characterization of an object deemed desirable if, and in so far as, it may be attainable, than of a rule intended to control rate making. ”