SURVEYING THE DESERT. 237
I had four assistants to help me with the rougher work, namely one man for the staff, a second to carry the telescope, and two to measure the intervals with the tape. A fifth man followed behind us with the four camels. It was of course a matter of indifference where we chose to start from, for in every case the altitude of any point along the whole of the line of traverse could be calculated from the water-level of the Kara-koschun. I started therefore at the spot where my tent was pitched at Camp No. CLIX. The difference of elevation, 2.282 m., between my point
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of departure and the point at which I terminated the survey possesses therefore only an ephemeral value, for neither point is definite. Had I chosen another point in the vicinity of Camp No. CLIX, a point that lay somewhat lower, the difference of elevation would have been still less, and if I had begun at the base of the clay tower the difference of level would have amounted to i o m. The uncertainty in the case of my terminal point, the water-surface of the Kara-koschun, is not so great, for it depends only upon its rise and fall according as the inflow varies. Nevertheless the indefiniteness with regard to the two terminal points of the survey, and the fact that neither can be regarded as a sure and fixed point, in no sense impairs, for the object I had in view, the value of the survey itself, for each and every point of the intermediate line maintains its relative value with regard to the line as a whole, and the line of traverse itself will always possess a fixed and certain position, no matter how much the water-level of the Kara-koschun may vary. But for a levelling back to my starting-point the water-level of the Kara-koschun would not have been suited just by reason of its oscillation, because its absolute elevation would in all probability have changed during the course of the survey.
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