which formed the text-book of the class, young Drummond sought and discovered a solution of a more simple character, and on a wholly original principle. Such was the merit of this bold innovation, that it replaced the solution of Hutton among the professors of Woolwich College, who were proud of their young pupil, and entertained the highest hopes of his future success as a military engineer. The same reflective independent spirit characterized his studies after he had left Woolwich to follow out the practical instruction of his profession. On one occasion his attention was directed to the various inventions by which the use of the old pontoon was to be superseded; and he contrived a model, which was reckoned a master-piece of ingenuity. It was, says his friend Captain Dawson, who describes it, "like a man-of-war's gig or galley, sharp at both ends, and cut transverely into sections, for facility of transport, as well as to prevent it from sinking if injured in any one part; each section was perfect in itself, and they admitted of being bolted together, the partitions falling under the thwarts or seats. The dockyard men, to whom he showed it, said it would row better than any boat except a gig; and it was light, and capable of being transported from place to place on horseback."
After having spent some time in training, both at Plymouth and Chatham, during which he embraced every opportunity of improving his professional knowledge, not only by books and the conversation of intelligent officers and scientific scholars, but also by a visit to France, to study its army of occupation and witness a great military review, Drummond was stationed at Edinburgh, where his charge consisted in the superintendence and repair of public works. But this sphere was too limited for his active spirit; and, finding little prospect of advancement in his profession, he had serious thoughts of abandoning it for the bar, and had actually enrolled his name as a student at Lincoln's Inn, when fortunately, in the autumn of 1819, he met in Edinburgh with Colonel Colby, at that time engaged in the trigonometrical survey of the Highlands. Delighted to have such an associate in his labours, the colonel soon induced the disappointed engineer to abandon all further thoughts of the study of law, and join him in the survey. As these new duties required Drummond to reside in London during the winter, he availed himself of the opportunity not only to improve himself in the higher departments of mathematics, but also to study the science of chemistry, which he did with his wonted energy and success. While attending, for this purpose, the lectures of Professors Faraday and Brande, his attention was called to the subject of the incandescence of lime; and conceiving that this might be made available for his own profession, he purchased, on his return from the lecture-room, a blow-pipe, charcoal, and other necessary apparatus, and commenced his course of experiments. These were prosecuted evening after evening, until he had attained the desired result. He found that the light derived from the prepared lime was more brilliant than that of the Argand lamp; and that it concentrated the rays more closely towards the focal point of the parabolic mirror, by which they were reflected in close parallel rays, instead of a few near the focus, as was the case with the Argands.
An opportunity was soon given to test this important discovery. In 1824, Colonel Colby was appointed to make a survey of Ireland, and took with him Lieutenant Drummond as his principal assistant. The misty atmosphere of Ireland made this survey a work of peculiar difficulty, as distant objects would often be imperceptibly seen under the old system of lighting; but the Colonel was also aware of the improved lamp which Drummond had invented, and
