In some places the light is placed in mid-stream, and perhaps mounted upon a massive, high, steel caisson, resting upon a concrete foundation, thereby proving immovable to the most powerful of ice-shoves. Or a large pier carried out in ferro-concrete and pyramidal in shape is used. In the case of the back light there is a skeleton tower, which structure is employed to gain the necessary height. This is carried upon a high, huge, solid plinth of concrete, even if built against the bank. The frazil ice dams the channel, causing the water to rise, and unless the foregoing precautions were adopted widespread damage would result. All the lights between the gulf and Montreal have to be protected in this manner, so that it will be seen that the adequate lighting of this waterway bristles with engineering difficulties of no light character, and is expensive. The Canadian Government also is responsible, to a certain extent, for the lighting of the Great Lakes, which is described in another chapter, where similar difficulties prevail. It has also a long stretch of the most rugged part of the Pacific coast to patrol, aggregating about 600 miles between Victoria and Vancouver to the Portland Canal, where Canadian meets Alaskan territory. This is a wicked coast, broken and battered, as well as flanked by an outer barrier of islands, recalling the Scandinavian Peninsula in its general topographical characteristics. During the past few years the necessity of lighting this seaboard adequately has become more pronounced, owing to the creation of the new port of Prince Rupert, a few miles below Alaskan territory, where the Grand Trunk Pacific reaches down to the western sea, and the growing sea-borne traffic with Alaska. The fact that a large portion of this navigation is maintained through the inside passages, bristling with sharp turns, narrow defiles, and jagged headlands, which for the most part are wrapped generally in fog, renders the lighting problem more intricate. Probably the most important light, and certainly the loftiest on the Pacific seacoast north of the Equator, is that on the summit of Triangle Island, British Columbia. It was built in 1910, and although the lantern itself is only 46 feet in height, the elevation of the headland brings the white group-flashing light of 1,000,000 candle-power 700 feet above the sea, giving it a range of thirty-four miles. Four flashes are emitted during each ten seconds, each flash lasting 0·28 second with intervening eclipses each of 1·28 seconds, with an eclipse between each group of 5·94 seconds.