midnight
remarked the Colonel , and the boys , who , for the first time , felt that they had really invaded the `` Terrible North '' of the explorers , gazed with new interest on the lush green meadows of the shores and the foliage of the tree-covered island . They ran on down the river , and an hour later landed at Fort Yukon , an abandoned military post , the most northerly point on the river , lying at the mouth of the Porcupine , the Yukon 's most important tributary . The voyagers left Fort Yukon the same afternoon and soon recrossing the Arctic Circle , continued on the dreary Yukon Flats , where the river broadened to more than thirty miles . As there was almost perfect daylight at midnight they proposed to sleep on board and continue the journey . In spite of the clouds of mosquitos , which managed to invade even the well-closed in cabin , they passed a restful night , the engine working perfectly , and soon passed into the narrower reaches of the Yukon , and in the early morning came to the town of Rampart . Here is a federal court which people come nearly a thousand miles to attend . There was also a telegraph station the end of the line to St. Michael 's and Colonel Snow stopped only long enough to send certain despatches to that point .