CHAPTER III.

THE ROYAL ENGINEERS.

IN 1815 Drummond entered the Royal Engineers, but for the next two years we learn little of his movements. In 1817 he joined the head-quarters at Chatham, and later on made a short trip to France "for the purpose of visiting the army of occupation, and attending one of the great reviews." 1

In 1818 he was at Chatham, engaged in routine work, and busy besides in directing the attention of the authorities to a pontoon which he had designed. This invention has been described by Captain, afterwards LieutenantColonel, Dawson. "The various inventions to supersede the use of the old pontoon led Drummond to consider the subject, and he made a model of a form like a man-of-war's gig or galley, sharp at both ends, and cut transversely into sections for facility of transport, as well as to prevent it from sinking if injured in any part. Each section was perfect in itself, and the sections admitted of being bolted together, the partitions falling under the thwarts or seats. The dockyard men and sailors to whom he showed it, said it would run better than any boat except a gig; and it was light, and capable of being transported from place to place on horseback." 2

The fate of this invention is not known. Little encouragement was given at head-quarters to men of genius. On March 27, 1818, Drummond wrote to his 2 Quoted in Larcom's Memoir.

1 Larcom.

mother: "I shall let you know what success my memoir 1 meets with. But there's no wish at the office to bring forward anything of that kind." Later on he writes again : "When I was at the Engineer office, a few days ago, I found Major Blanchard's model, with his memoir and a letter addressed to General Mann, in the ante-room. The box had been opened, only one of the models taken out; his memoir apparently had not been looked into, for within the first leaves was the letter I have just mentioned, unopened." In May, Drummond brought his model and memoir to London. The model, he tells us in a letter to his mother, written May 31, "experienced a gracious reception." But at this stage we lose sight of the invention. Drummond regarded the matter with his accustomed calm. He wrote to his mother: "If the plan is not approved, I may safely say it will not be laughed at. Whatever, then, may be the result it may be for good-it cannot do me harm."

An incident in his life at Chatham deserves to be recorded, as showing the presence of mind and generous nature of the man. "He was charged with the construction, for practice, of a bridge of casks in the rapid current of the Medway, at Rochester Bridge, and having previously made piers of the casks in the still water above the bridge, it was necessary to move them through the rapids to get them below the bridge. The piers were, as usual, lashed two and two for security; but one remained, and as its removal was like to involve some danger, Mr Drummond determined to go on it himself. There were two soldiers on the pier, one of whom showed a little apprehension at setting off. Drummond placed this man next himself, and desired them both to sit quite still. They passed through the arch in safety, when the man

It was the custom to send a memoir, with the model of an invention, to the head office.

who had previously shown apprehension, wishing by activity to restore himself to his officer's good opinion, got suddenly up to assist in making fast to the buoy; in an instant the pier upset, all hands were immersed in the water, and the man who had caused the accident, being on his feet, was thrown from the pier and drowned. Mr Drummond and the other man clung to the pier, and Mr Drummond afterwards described his sensations, when finding his body swept by the current against the under side of the pier. His last recollection was a determination to cling to one side of it, in hopes the depression of that side might be noticed. This presence of mind saved him and his comrade; for, as he expected, a brother officer (Fitzgerald) noticing the lowness of one side, sprang from a boat upon the other, and immediately the heads of poor Drummond and the sapper appeared above the water. Drummond was senseless, with the ropes clenched firmly in his hands."1

In July 1818 Drummond was stationed at Edinburgh, where he found the time hanging so heavily on his hands, that he resolved to give up the Engineers and join the Bar; "with this view he had actually entered his name at Lincoln's Inn." But in 1819 he met Colonel Colby, who was then engaged on the Ordnance Survey in Scotland. In 1820 Colby was appointed chief of the survey. He asked Drummond to join him in the work. Drummond consented, gave up all notion of joining the Bar, and took the first step in a career which has made his name memorable.

1 Larcom.

2 Ibid.

CHAPTER IV.

THE DRUMMOND LIGHT AND HELIOSTAT-THE

ORDNANCE SURVEY IN IRELAND.

THE Ordnance Survey of Great Britain began in Scotland after the rebellion of 1745. The object was to obtain "accurate knowledge" of the Highland districts. The work was badly done, and the results were not published. In 1763 the subject of a general survey of the island was broached, but no steps were taken to carry it out. Finally, in 1783, "a representation was made from France to our Government, of the advantages which the science of astronomy would derive from the connection, through trigonometrical measurements, of the observatories of Greenwich and Paris, and the exact determination of their latitudes and longitudes. The French had by this time carried a series of triangles from Paris to Calais, and what they proposed was that the English should carry a similar series from Greenwich to Dover, when the two might be connected by observations from both sides of the Channel. The scheme was approved of by George III., and the English survey begun by the measurement of an initial base line1 at Hounslow Heath by General

1 "A base-line is an initial measured line, whose length is assumed as the unit to which all other distances calculated in the survey are temporarily referred. The exact length of the base in yards, feet, and inches being known, these other distances admit at once of being reduced to yards, feet, and inches. But any error in measuring the base must enter into all of them. For convenience in measuring any large tract of country-in other words, in constructing a Trigonometrical Survey-it is necessary that the length of the base should be a considerable multiple of the standard unit of length, several thousand yards at least; and for the accuracy of the survey, it is necessary that this length should be measured most exactly."--McLennan.

Roy the foundation of the triangulation since effected of Great Britain."" 2

The work was now entrusted to the Royal Engineers, and from 1783 to 1790 proceeded steadily under the direction of General Roy. In 1790 General Roy died, and was succeeded by Colonel Mudge. In 1791 Hounslow base was re-measured. Between 1792 and 1794 the triangulation was extended southwards to the Isle of Wight. Between 1794 and 1801 it embraced Salisbury Plainwhich was taken as the base-Dorset, Devon, Cornwall, and the Scilly Isles. In 1801 a new base was measured on Misterton Carr in North Lincolnshire; and in 1806 part of North Wales was surveyed. In 1817 Scotland was

1 "The base being measured, the next set of operations, those of the triangulation, commence. Some object is fixed upon, which is considerably farther from either end of the base than the length of the base line. Theodolites, with delicately graduated circles, capable of measuring angles to an extreme nicety, are then placed centrally over the dots which mark the extremities of that line, and their telescopes are directed to one another until, as it has been graphically said, 'they look down the throats of each other.' The telescopes being in this position, are clearly both of them directed along the base line. Each of them being now turned round till it looks straight at the object which has been fixed upon, the instruments are clamped, and the angles through which the telescopes have been turned are read off on the graduated circles. The angles are thus ascertained, which lines, drawn to the object from the extremities of the base, make with the base line. The object, in short, is made the summit of a triangle in which two angles, and the length of the side between them, are known. Its distance from either end of the base can thus be ascertained by computation, and made available as a new and larger base. Thus,' says Sir John Herschell, in a paper in which this subject is handled with his usual lucidity, the survey may go on throwing out new triangles on all sides, of larger and larger dimensions, till the whole surface of a kingdom, or a continent, becomes covered with a network of them, all whose angular points are precisely determined. The strides so taken, moderate at first, become gigantic at last; steeples, towers, obelisks, mountain cairns, and snowy peaks, becoming in turn the stepping-stones for further progress, the distances being only limited by the range of distinct visibility through the haze of the atmosphere.' In mapping a country, after the network of great triangles has been thrown over it, the great spaces comprehended by them are filled in by a system of smaller triangles so as to carry the survey to any degree of minuteness that may be required." — McLennan. Sir John Herschell, "Familiar Lectures on Scientific Subjects."

2 McLennan.