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392 without the necessity for intermediate readings – was undoubtedly a beautiful principle as far as it went, but in its application it was designed simply to counteract faulty graduation of the circle. Yet it was apparently the ingenious neatness of this principle which had so fascinated the foreigners, and brought this construction of instrument into such favour with them. But Troughton insisted that this was the "little all" of advantage it could properly lay claim to possess over an altitude and azimuth instrument of English style.

For the last two or three years of General Mudge's connection with the National Survey, his health, which had suffered from exposure and hard personal exertion, became very indifferent, and upon Colby, therefore, devolved at this time the charge of the bulk of the work of the Department.

In May 1819 two young lieutenants of Engineers, Dawson and Robe, joined the Ordnance Survey, and with a party of artillerymen, selected from his Majesty's Royal Regiment, set out forthwith for Scotland to begin the season's work on the northern spurs of the Grampians. Of the former I shall have something more to say hereafter; but meantime we will glance at an interesting diary he kept, describing the camp-life and goings-on during this year of himself and his comrades on the "great trig" in the wilds of the Scotch Highlands. A whiff of the mountain air, a peep at the little encampment high up in the mists and snow among the blue hares and ptarmigan, and a tramp across country with Colby and his officers of the sort these state-toilers were wont to take day after day over glen, flood, and fell, in those times of the Survey, will probably not be unwelcome features for the reader's contemplation in this our review.

I have spoken of Colby's remarkable activity and working power, notwithstanding the way in which the severe accident he sustained in early life had so handicapped him for his duties. It may be added that he was not less conspicuous for endurance of fatigue and exposure, as well as hardness, and a kind of Spartan frugality when necessary – all invaluable accompaniments to his untiring industry. Of this we shall have illustration.

In June 1819, Colby started from London to join the "trig" camp on Corriehabbie, a lofty offshoot of the Banffshire Grampians, overlooking the Duke of Gordon's Glenfiddich deer-forest. We can picture him in the long journey by mail-coach from the metropolis to Huntly, by way of Aberdeen, on an outside seat; the march of the surveying-party up Glenfiddich, shoving or dragging up their baggage-waggons with the aid of guy-ropes to the highest point accessible to anything on wheels; and thence the loads, laboriously carried up the rest of the way, partly on horse- or pony-back, pannier-fashion, partly on the backs of the men, over plashy peat-hags or rugged boulder-strewn, acclivities. Then the setting out of the camp at the summit of the mountain: sites for the dwelling tents, the watch tent, the cooking caboose in as sheltered a nook as practicable, the temporary observatory where the great and precious instrument, with its appara-