“ Moving engines and cars to and fro over such a place makes it one of danger. Any one of several forms of corrective regulation might be applied. To illustrate: The city might call on the railroad company to construct and maintain a viaduct over the crossing or a tunnel under it, or might lay on the company the duty of maintaining watchmen or flagmen at the crossing. What it actually does by the ordinance is to call on the company to remove the track from the crossing and avail itself of other accessible and fairly convenient means of getting cars to and from its track east of the crossing. ”

“ The scope of the power and instances of its application are shown in the decisions sustaining regulations (a) requiring railroad companies at their own expense to abrogate grade crossings by elevating or depressing their tracks and putting in bridges or viaducts at public crossings, Northern Pacific R. R. Co. ”

“ Ct. 696, 41 L. Ed. 1160; and (d) requiring a gas company whose mains and pipes were laid beneath the surface of a street under an existing franchise to shift them to another location at its own cost to make room for a public drainage system, New Orleans Gas Co. ”