SEEING SIXTY MILES
United States Engineers Did it on Lake Superior
The lake survey parties under Assistant Engineers Haskell and Russell have recently measured some angles of the triangulation, which involved seeing across Lake Superior from Gargantua to Crisp's Point, a distance of over sixty miles. At Gargantua the old station to which connection had to be made was about 410 feet and at Crisp's Point the station was about 250 feet above the lake. On account of the curvature of the earth, a straight line connecting the two would pass under the water for a considerable part of its length. At Crisp's Point an observing station 100 feet high was built and a straight line from the top of it would still pass under the water in the middle of the lake. Atmospheric refraction, however, causes a bending of lines of sight so that distant objects are apparently lifted up - but even with the average refraction conditions it would have been impossible to see one of these stations from the other. If this line could not be seen across, however, it would be necessary to occupy three additional stations in the Canadian wilderness east of Lake Superior, and the cost of the work would have been almost prohibitory. It was known, however, that the refraction sometimes becomes excessive, especially on Lake Superior, and both stations were occupied with the hope that these extraordinary conditions would occur and permit the line between the two stations to be seen across. Accordingly, Mr. Haskell's party occupied the station at Gargantua, and Mr. Russell's party occupied that at Crisp's Point.
For two weeks the necessary conditions were patiently waited for, but finally the smoke cleared away, and the sun came out so that the mirrors at each station that had to be used to flash light from one to the other, could be brought into play. The sun flash was finally seen and the angles were soon measured.
The sun flash seen at one station from the other presented numerous peculiarities. It would sometimes appear single, then would split up into three, four, and even five different flashes - one over the other in a vertical line. Sometimes flashes would appear white, at others they would take the different colors of the rainbow.
The line could be seen across generally after a storm, when the wind changed to northwest and cleared the atmosphere out. The conditions were the same as those attending the mirage which is frequently seen, especially on Lake Superior.