Page:Mongolia, the Tangut country, and the solitudes of northern Tibet vol 1 (1876).djvu/184

 Fortunately I was never surprised with the map, and no one ever knew that I was sketching my route. My surveying instrument was a Schmalkalder compass, which is usually fixed on a tripod stand; but as this would have excited suspicion and interfered with the success of the expedition, I determined to do without it, and steadied the compass in my hands. If the needle continued in motion for more time than I could conveniently spare, I read off the mean degrees between the extreme points of oscillation. In measuring distances I reckoned by the number of hours of travel and our rate of progress. The scale of my map was 10 versts to the inch. I carried a small field-book for noting all conspicuous objects, as it is never safe to trust to one's memory in such work, where accuracy is of the highest importance. At the end of every day's journey I transferred the field survey to my diary, keeping the map on ruled sheets carefully stowed away in one of the boxes.

My plan was this: After taking bearings in the direction we were going and noting the time by my watch, I drew a line in my pocket-book corresponding as nearly as possible with that of our march; at the end of it I entered the degrees and marked off the intersections with figures in their regular order.