Page:Popular Science Monthly Volume 76.djvu/93

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HE claim to have reached the north pole, a point sought for several hundred years by many intrepid explorers, must, of course, be substantiated by adequate proof; and it may interest readers of this magazine to know what kind of proof is possible and necessary, and what observations the explorer must make to determine his geographical position when he is in the neighborhood of the pole.

Let us say, in the first place, that neither photographs, which only show the condition of the ice, but do not indicate whether they were taken near the pole or several hundred miles from it, nor the testimony of human beings, gives any evidence whatever that an explorer has been to the pole. Persons who were not actually with the explorer can only express their confidence in his good faith, in his knowledge of the proper astronomical observations to be made, and in his ability to make them with sufficient accuracy. Persons who accompanied him could only vouch for the fact that he did not remain in camp at a comfortable distance from the pole and manufacture observations, but that he actually traveled in the general direction of the pole, that on a certain date he claimed he was there, and that he made frequent astronomical observations on the route.

The only evidence which can at all satisfactorily show that an explorer has been near the pole is that afforded by observations on the sun or stars, capable of determining his successive positions at the times they were taken. Other evidence might prove the negative; such as inconsistencies in the narrative, inadequate time or insufficient food for the distance traveled, the description of phenomena which could not have been seen at the place where the explorer thought he was; and so on. It is impossible to foresee the many discrepancies which might show that an explorer has not been to the pole; they will not be considered here, as this article is not controversial, but merely aims to set forth, as simply as possible, what kind of observations must decide the claim of having reached the pole.

Confining our attention for the moment to observations on the sun, for the sake of simplicity of statement, we may say that the determination of one's position anywhere on the earth depends upon measuring the altitude of the sun above the horizon at two times, the second being, preferably, after the direction of the sun has changed by 90°. This becomes clear if we consider Fig. 1. Let us suppose the sun is