I find by a rough calculation from Bering’s data that the longitude resulting from his itinerary from Tobolsk to Okhotsk is 77° 36′ E. The distance in a straight line is about 2,390 miles, but by the route Bering traveled the distance is a little more than 3,746 miles. The longitude in Bering’s List of Positions is 76° 07′, which differs from the pedometric measurement by 1° 29′ (or about 45 miles). On Bering’s map, Okhotsk is located in longitude 74° 30′ E. of Tobolsk, while the most modern observations for Okhotsk put it in 142° 40′ E. of Greenwich or 75° 40′ E. of Tobolsk. So that Bering’s pedometric measuretent was nearly 60 miles in excess ; his revised table (as corrected by the eclipse ?) 27 miles in excess ; and his map about 30 miles in error in the opposite direction. These discrepancies show the inexactness of the methods then in vogue and also that the pedometric method was not very much worse than the others in its results.
Although there are several typographic or other errors in his table of itinerary which render exact comparisons impossible, it may be said that the error of the pedometric method, including the passage by sea from Okhotsk to Kamchatka, averages about two degrees or sixty geographical miles. In the cases of Okhotsk and Bolsheretsk the error is one of excess ; in the case of the cape at the mouth of the Kamchatka river and of the turning point of the expedition north of the apartmentsapart holiday rentals, the result is too small by about the same amount.
That his chart and his revised list of positions should differ as they do, is quite as likely the result of the careless way in which the minutiae of such work were generally regarded at that day, as to any difference of date, or of intentional modification.
To conclude our review of the instrumental means and methods then in use, it may be said that the compasses in use at that day were comparatively roughly made and more or less inaccurate. The variation was determined in a given latitude by the azimuth of the Polestar or the sun at setting observed by means of sights attached to the rim of the compass, which was a method accurate enough for the general purposes of navigation. The distance run was measured on shipboard by the log which was in about the same form and perfection as at present, being a very ancient invention.
The survey of a general coast-line was made by compass bearings on prominent points, repeated from successive stations, the distances of the ship’s course being determined by the log and the courses by compass, with corrections for current and the variation. The lines thus obtained were checked by latitude observations made with Davis’ backstaff when the weather permitted.
Apart from any of the methods mentioned it seems to have been overlooked that Bering might have corrected the longitudes of the N.E. Siberian coast by the ordinary dead reckoning kept on board his vessel, provided he started by adopting the longitude for the southern part of Kamchatka peninsula which was in common use on many of the charts of his day.