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the guns on martello towers, in the batteries, or wherever they were to be found, the indiscriminating dogs laid hands on the sacred pedestals, and conveyed them to an ordnance store! I believe, however, that beneath the guns oaken piles were driven, and these it would not be difficult to find. The marks on Hanger Hill Tower and Shooter's Hill Tower are preserved. With respect to the extremities of the Irish base, the most satisfactory precautions have been taken to secure them. The bases, about 3 feet under the surface, consist of four slabs, about 3 inches thick, and 7 feet long by 31 broad. These are laid transversely, while longitudinally two blocks of compact sandstone, weighing about (I think) 17 or 18 cwt., and being somewhere about 4 feet square, are placed above themthe whole firmly cemented with Roman cement. The surface is level with the surface of the ground, and the soil is very firm and secure. They were placed several weeks before they were used, to get rid of any little settlement to which they might be liable. The ground has, however, been purchased, and enclosed by the Ordnance.
" There is little to attract attention, and there is sufficient strength to resist any ordinary attempts of the country people to remove them, supposing them to be so inclined, which I believe they are not. Nothing but the mandate of Captain Rock or Dan O'Connell would expose them to destruction. I am ashamed at having detained the sketch so long. It is safe, however, and shall be sent to you as soon as I return.
I have now endeavoured to answer your questions, very imperfectly I admit, but as well as my present situation and occupations will admit of my doing. If you require anything more, I shall be most happy to procure it on my return to town, which will probably be in a fortnight. At present I am engaged making some inquiries for Government, which occupy my whole time; but I assure you that you do me a favour by affording me any opportunity of showing, though in a very humble way, the grateful sense I entertain of your kindness on many occasions.-Believe me, my dear sir, most truly yours,
The actual measurement of the Lough Foyle base commenced on the 6th September 1827, and was continued without intermission till the 25th of October, when, in consequence of the advanced state of the season, it was deemed advisable to suspend the work till the following year. The measurement was resumed on the 7th July 1828, and continued till the 25th of the same month, when it was suspended, in consequence of the crops being on the ground over which the line lay. It was resumed after the harvest, on the 13th of September 1828, and completed on the 20th November of the same year.
THE ORDNANCE SURVEY; MR DRUMMOND'S HEALTH; THE
DRUMMOND LIGHT AND LIGHTHOUSES ; A VISIT TO THE KING , LORD BROUGHAM.
AFTER the measurement of the Lough Foyle base, Mr Drummond remained for some time in Ireland, the head-quarters of the Survey being now in Dublin. In December 1828, and January 1829, he was engaged, along with Lieutenant Murphy, in comparing the measuring bars and the standards, and testing the compensation microscopes; which work they resumed and completed in the following autumn. During a portion of the summer, they were occupied in observations for the triangulation in the vicinity of the base.*
The anxiety and exposure attending the operations in 1828 had seriously affected his health-the second, if not the third time, that a severe illness had sprung out of his devotion to the service. He suffered much, as in the winter of 1825, from palpitation and sleepless
* The observations made at Minearney by Messrs Drummond and Murphy in June 1829 are given in the Appendix to Yolland's
Account," where will also be found the results of the comparisons referred to, pp. 20, 21, and 22. In February, March, and April 1830, Mr Drummond was engaged in a similar set of comparisons.Ibid. pp. 15, 19. The last time he took part in experiments of this kind was in the spring of 1833, when, along with the Rev. R. Sheepshanks and Mr Simms, he was engaged in ascertaining the expansions of the Royal Society's brass scale.--Ibid. p. 12.
He refers to this illness in a paper read before the Royal Society, June 17, 1830, “ On the Illumination of Lighthouses.” The Trinity House Corporation had resolved, as early as 1826, to give his light a trial as soon as the apparatus should give a steady continuance of light, and be fit to be entrusted to ordinary attendants. “ The survey of Ireland, however,” he says, “ had just been commenced; and being employed on that service, I found it impossible to continue my experiments, in the first instance, from constant occupation and absence from London, and latterly, from a long and severe illness, the consequence of a very laborious and anxious duty in Ireland. During the last winter, however, I was again able to return to the subject.” The reference is to the measurement of the base, in the course of which he had suffered much from inclement weather, and from frequently standing in deep water (as in crossing the river), intent on the measurements, and regardless of himself.
This, as I have said, was the second, if not the third illness suffered in the service. Miss Drummond speaks of a severe illness, the date of which I am unable to fix. He occupied, she says, a hill-station in Ireland. The weather became tempestuous, and the station untenable; yet he held to his post at first from a sense of duty, but afterwards from inabilty to leave it. A chance visitor to the station, who happened to be a medical man, discovering his condition, hastened for assistance to the house of a landed proprietor in the neighbourhood. He described the camp hut as filled with water, and Drummond as certain to die if allowed to remain in it. The gentleman appealed to at once made for the hill, accompanied by his son. They found Drummond very ill, and had to carry him to the carriage, where they rolled him in blankets which they had provided. Having taken him home, they nursed him with the greatest care and kindness, for the six weeks which passed before he was able to return to his mother's house. Miss Drummond's recollection is, that the name of these hospitable people was Mac Causland. She adds, “He was about a fortnight with us before he was able to go out just a little. I remember the Survey people wanted to stop his pay. He wrote them a thundering letter. Was there ever anything equal to this ?' he said; they throw away thousands of pounds, and would rob me when I am become disabled in their service.” He heard no more of the threat to "suspend payments.” It seems impossible that this account can refer to the illness which followed the sojourn on Slieve Snaght. Larcom thinks the time must have been the close of the first season at the Base.
He arrived in London late in the autumn of 1829, to prosecute his design of fitting the lime-light for light
He had been engaged in improving the apparatus for this purpose in the spring of 1826, and may then have got it nearly into shape; he was certainly ready to bring it into use very soon after his return to town. Before the end of the year he was busy with experiments instituted by order of the Trinity House, for ascertaining the relative merits of the different methods of illumination in lighthouses. Some of these were carried on at the Trinity House ; others at a small lighthouse at Purfleet, which had been placed at his disposal by the Corporation. They were conducted under the direction of the Committee for the Management of the Lighthouses, and they fairly established the superiority, at least in brilliancy, of the Drummond Light over all others.