reconnaissance" of Ireland made by Colby and Drummond in the autumn of 1824. They traversed the country from north to south, fixed upon the mode of conducting the survey, and selected the stations for the great triangulation, as well as the most fitting place for measuring a base. Enough has been seen of Colby's manner of making a reconnaissance of a country, to enable the reader to judge what exposure and fatigue were suffered in this expedition.

In the autumn of 1825 the triangulation commenced on the Divis mountain, near Belfast. Officers were sent into Cumberland and the Isle of Man to recover and erect marks on the old stations there as points of observation from Divis for the connection of the Irish and English Surveys. While they were on this duty, Drummond, with his heliostat, light apparatus, and a complete observatory of meteorological and other philosophical instruments, was encamped on Divis preparing the station for the great theodolite. On the 23d of August a conspicuous object was placed on the summit of Slieve Snaght, the highest hill of Innishowen, about 2100 feet above the sea. This was an important point in the triangulation which connects the north of Ireland with the western islands of Scotland, and it was necessary that it should be observed from Divis. The party of observers on Divis were in camp as early as the date of marking Slieve Snaght. They continued there till the 26th October without being able to make the necessary observation. The mountain continued enveloped in a haze so impenetrable as to render unavailing every effort made for the purpose. All this time it seems not to have occurred to put either the heliostat or light in use. But now, late as it was in the season, Colonel Colby determined that Drummond

should ascend the mountain, and attempt to overcome the formidable obstacle to the completion of the observations by the aid of his apparatus. He did so, and with what success we may see in the narrative of General Larcom :-" Mr Drummond took the lamp and a small party of men to Slieve Snaght, and by calculation succeeded so well in directing the axis of the reflector to the instrument on Divis, that the light was seen, and its first appearance will long be remembered by those who witnessed it. The night was dark and cloudless, the mountain and the camp were covered with snow, and a cold wind made the duty of observing no enviable task. The light was to be exhibited at a given hour, and to guide the observer, one of the lamps formerly used, an Argand in a lighthouse reflector, was placed on the tower of Randalstown Church, which happened to be nearly in the line at fifteen miles. The time approached, and passed, and the observer had quitted the telescope, when the sentry cried, "The light!' and the light indeed burst into view, a steady blaze of surpassing splendour, which completely effaced the much nearer guiding beacon. It is needless to add that the observations were satisfactorily completed, the labours of a protracted season closed triumphantly for Drummond, and the Survey remained possessed of a new and useful power."

This year's operations did grievous mischief to Mr Drummond's health. A residence on the top of Slieve Snaght at such a season of the year might have tried one more robust. He was borne up for the time by the excitement attending the first practical test of his inventions, only to suffer the more severely afterwards. With what joy he hailed the success of his operations on the lonely mountain we fortunately may see from a

letter written in his hut on the night of November 11, 1825. In the moment of success his first thought was to communicate the pleasure of it to his beloved mother:

"SLIEVE SNAGHT, "Friday night, Nov. 11, 1825.

"MY DEAR MOTHER,-What has become of Tom? and why does he not write? are questions which you may of late have not unfrequently asked, and, I dare say, without any oue being able to give a very satisfactory answer. Why, then, I am perched upon the top of Slieve Snaght (the Snowy Mountain), 2100 feet high in the centre of Innishowen, the wildest district in Ireland. Since the 23d of August, when a pole was placed on this hill, we have endeavoured to observe it from Divis, near Belfast, on which our tent was placed, but in vain. Constituting an important point in the triangulation of Ireland, our sojourning on the hill-tops has been prolonged to an unusually late period, in the daily hope that it would have been visible. Disappointment, however, was our lot, and the weather becoming broken and tempestuous, the colonel determined upon breaking up the camp and retiring to winter quarters. Just at that moment a letter was received from one of our officers encamped on Knock Layd, a hill about 40 miles distant, giving a splendid description of the solar reflection which I had exhibited to him, and which had been seen through a very hazy atmosphere, and seen for a time with the naked eye; and one of our officers tells me that the country people, whom curiosity had attracted to the spot on hearing the distance at which it was placed, actually raised a shout of exultation at its brilliant appearance. This being known at Divis, it became a question whether Slieve Snaght should be attempted at this season; and after due deliberation, it being decided that it should, I made a forced march upon this place, and, leaving Belfast on Tuesday forenoon, slept on this mountain on Thursday night, the 27th October, our tents erected, and hut constructed, and all the apparatus of the lamp ready for work. For the first week our life was a struggle with tempest-our

tents blown down, our instruments narrowly escaping, and ourselves nearly exhausted. At length, by great exertions, we got two huts erected, one for the seven men who are with me, the other for me-a lonely and humble dwelling, it is true, and now that the snow has fallen, so completely covered up that it is not very easily distinguished; nevertheless affording good shelter, warm and comfortable, and, at the present moment, with a good peat fire. The weather at length improved, and Wednesday the 9th instant brought our exertions to a successful termination. The colonel, after making the necessary arrangements, took his departure for London on the very day I arrived here, leaving Murphy and Henderson to keep a constant look-out for the lights. Their assiduity has been unremitting, and their fatigue by incessant watching not a little. This day brought me a letter from Murphy, which begins thus: 'Your light has been most brilliant to-night for three hours and twenty minutes, as was your solar reflection to-day. I began by giving you the pleasing intelligence in a condensed form, but now I must most heartily congratulate you, my dear friend, on the complete success which has thus crowned your very ingenious and laborious exertions for the good of the service. I trust they may eventually prove as beneficial to yourself. I really feel sincere pleasure in making you this communication. I will now give you some details. I first had notice of your appearance from Elliot, who called out that he saw the light, and in fact, though five times more remote, you were much brighter and larger than the Randal's tower reflector.' I have given you a long extract, because I think it will interest and please you. I have only to inform you now that the distance in a straight line between the two places is about 67 miles. I had a letter from the colonel to-day in London, very anxious to know the result of our labours. To-morrow I commence my retreat; on Monday I shall be in Derry, where I shall have to remain a day. . . . From Derry I proceed to Belfast, where I shall be detained. two or three days, and then I make direct for Edinburgh. Belfast I entreat you to let me hear from you, and I am anxious to hear how Eliza bore the journey from Callendar, and how

At

the house is. My last intelligence is her own letter, which I received about the 19th ultimo, on the evening succeeding a gale of wind, which overthrew two of our marquees, and set fire to our cooking-house. I have written you, my dear mother, a long and gossipping letter, and it being now three o'clock in the morning, it is fit that I should stop. To John and Eliza my kindest love, and to Eliza my best thanks for her kind letter. It may amuse my aunt to read this letter to her, and tell her that I add my best regards.-And now, my dear mother, believe me your affectionate son,

"T. DRUMMOND."

This chapter, composed mainly of quotations, must be concluded by another from the Memoir of General Larcom :-

"The triumphant success which attended the lamp and heliostat at the close of 1825, was purchased at the cost of a severe illness. A mountain camp, at an altitude of two thousand feet in the winter of these climates, is, under any circumstances, a severe trial; but Drummond and his little party were peculiarly exposed. Few in number-being merely detached from the general camp at Divis—they were ill able to buffet with the storms of these wild regions; and the tents were so frequently blown down, that after the first few days they abandoned them, and constructed huts of rough stones, filling the interstices with turf. Such, without the additional luxury of a marquee lining, was the study and laboratory on which depended the success of the new instruments. Here were to be performed the delicate manipulations their adjustment required. Here was to be manufactured the oxygen destined for the portable gasometer; and, cowering over the fire, or wrapped in a pilot coat, was Drummond day and night at work. A frame and system attenuated by fatigue and excitement were ill able to bear up against such exposure. He struggled to the last; but no sooner had his efforts been crowned with success than he sank, and a severe illness compelled him to return to Edinburgh, to the care of his family and friends."