A new map of the Indus and Punjab Rivers from the sea to Lahore seems to require some notice explanatory of its construction, and I have to offer the following observations on that subject:—

The River Indus, from the southern direction in which it flows in its progress to the ocean, presents few difficulties to the surveyor, since an observation of latitude serves to fix the daily progress in the voyage, and its comparatively straight course admits of easy delineation. The map rests on a series of observations by the stars. I should have preferred altitudes of the sun; but, with a people so suspicious as we encountered, it was impossible to use an instrument in daylight, and I should have required to halt the fleet twice to procure equal altitudes, since the sun was south of the equator during the voyage. Many of the large places, such as Tatta, Sehwun, Ooch, Mooltan, &c., where we necessarily halted, have been laid down from a mean of eight or ten stellar observations.

The longitude and general delineations in the curvature of the river rest on a minute protraction of its turnings, observed with care every half hour, and sometimes oftener, with the approved compass by Schmalcalder. The attention given to this important portion of the undertaking may be imagined, when I state that my field books exhibit, on an average, twenty bearings each day from sunrise to sunset. I was early enabled to rate the progress of the boats through the water, by timing them on a measured line along the bank, and apportioned the distance to the hours and minutes accordingly. We could advance, I found, by tracking, or being pulled by men, at one mile and a half an hour; by gentle and favourable breezes at two miles, and by violent winds at three miles an hour; while any great excess or deficiency was pointed out by the latitude of the halting place.

The base on which the work rests, is the towns of Mandivee and Curachee: the one a seaport in Cutch, and the point from which the mission started; the other a harbour in sight of the western mouth of the Indus, which we saw before entering the river. Mandivee stands in the latitude of 22° 50´, and Curachee in 24° 56´ north; while their longitudes are respectively in 69° 34´, and 67° 19´ east, as fixed, in 1809, from the chronometers of the Sinde mission by Captain Maxfield.

Assuming these points as correct, the line of coast intermediate to them has been laid down from my own surveys in Cutch; while that of Sinde rests on observations of the sun’s altitude at noon and the boats’ daily progress, determined by heaving the log hourly. We sailed only during the day, and at all times along shore, often in a small boat, and were attended by six or eight pilots, who had passed their lives in the navigation of those parts.

The great difference in the topography of the mouths of the Indus, from what is shown in all other maps, will no doubt arrest attention; but it is to be remarked, that I call in question no former survey, since the river has been hitherto laid down in this part of its course from native information; and I can bear testimony to the correctness of such portions of the Indus as were actually traversed by the mission of 1809. From the jealousy of the Government of Sinde, we had to pass up and down the coast no less than five times, which gave ample opportunities to observe it; and I have a strong fact to adduce in verification of the chart as it now exists. On the third voyage we ran down so low as the latitude of 20° 30´ N., and were out of sight of land for six days. At noon, on the last day (17th of March), while standing on a due northerly course, I found our latitude to be 23° 50´, or a few miles below that mouth of the river which I had resolved to enter. I immediately desired the pilots to steer a north-easterly course for the land. We closed with it at sunset, a couple of miles above Hujamree, the very mouth of the Indus I wished to make. At daylight we had had no soundings in fifty fathoms, at seven A.M. we had bottom at forty-two fathoms, and at eleven in thirty-four. By two in the afternoon we were in twenty-one fathoms, and at dusk anchored in twelve feet of water, off Reechel, having sighted the land at half past four.

In delineating the Delta of the Indus below Tatta, I have not only had the advantage of sailing by a branch to that city, but approached it on land by one route, and returned by another. I also ascended the Pittee, or western mouth of the Indus, for thirty miles. The opposition experienced from the Sinde Government gave rise to these variations of route: they long tried to impede our progress; but the result of their vacillation has happily added to our knowledge of their country, in a degree which the most sanguine could not have anticipated. In addition to my own track, I have added that of the Sinde mission, from Curachee to Hydrabad, and thence to Lueput in Cutch. My own surveys in Cutch, which extend high up the Koree, or eastern branch of the Indus, together with every information, compel me to place the Goonee or Phurraun River (which is the name for the Koree above Ali bunder), in a more westerly longitude than in the maps hitherto published. Sindree and Ali bunder lie north of Nurra in Cutch, so that the river cannot extend so far into the desert as has been represented.

From Hydrabad upwards, and, I may add, in all parts of the map, the different towns rest on the latitudes as determined by the sextant. Most of them are in a higher parallel than in the maps, but it was satisfactory to find, on reaching Ooch, that the longitude of that place, as taken from my own protraction, coincides pretty well with that which has been assigned to it by Mr. Elphinstone’s surveyors, who must have fixed it from Bhawulpoor. This was not the case with Bukkur; but, as the latitude of that place was twenty-two minutes below the true parallel, I have reason to be satisfied with the result above stated. I likewise found that the Indus receives the Punjab rivers at Mittun, in the latitude of 28° 55´, instead of 28° 20´ north, as given in the map of the Cabool mission: but no one can examine that document without acknowledging the unwearied zeal of its constructor, and wondering that he erred so little when he visited few of the places, and had his information from such sources.

The Punjab rivers have been laid down on the same principle as the Indus. The Chenab (Acesines), which has been erroneously styled Punjnud, after it has gathered the other rivers, is very direct in its course; but the Ravee (Hydräotes), on the other hand, is most tortuous, and appears in its present shape after incredible labour for twenty days spent in its navigation. The latitude of its junction with the Chenab, and that of the city of Lahore, which stands in 31° 35´ 30´´ north, and in 70° 20´ east longitude, have materially assisted me in the task. I have also placed the confluence of the Jelum, or Behut (Hydaspes), with the Chenab, twelve miles above the latitude in which it has hitherto stood. The survey eastward terminates on the left bank of the Sutledge (Hesudrus), with the British cantonment of Lodiana, which I find stands in 30° 55´ 30´´ north latitude. I have used the longitude of the latest and best map, and placed it in 75° 54´ east.

With the Indus and Punjab Rivers, I have embodied a survey of the Jaysulmeer country, which was finished in the year 1830, when I visited Southern Rajpootana with Lieut. James Holland. The province of Cutch, with the configuration of the Run, rests on my own surveys made in the years 1825, 1826, 1827, and 1828.[15]