ness. 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 lighthouse use. 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.

The original light apparatus had been designed for the Survey. Portability, rather than economy, had been studied in its construction. The ball of lime-from which when intensely ignited the light was derived— was heated by means of a stream of oxygen directed through a flame of spirit of wine. This source of heat was expensive, and, in considering the changes now to be made, economy was a primary object. For the alcohol Drummond substituted hydrogen gas, which proved not only much more economical, but productive of a considerable increase of brilliancy in the light.

The new apparatus was exceedingly ingenious. The oxygen and hydrogen gases, proceeding from separate gasometers, arrive at a small chamber, where they are made to mix. Into this chamber the oxygen gas is projected horizontally through a series of very small apertures, the hydrogen gas rising into it vertically through a series of similar apertures. From this the united gases pass through two or three pieces of wire gauze, and, being thoroughly mixed, issue through two jets against the lime ball in the focus of the reflector. To prevent the wasting of the ball opposite the two jets, and at the same time to diffuse the heat more equally, the ball is made by the apparatus to revolve once in a minute. Notwithstanding this movement, the heat cuts a deep grove in the ball, and it becomes necessary to replace it by a new one every three-quarters of an hour. As it would be unsafe in a lighthouse to intrust the replacing of the ball to an attendant, the apparatus is so contrived that it effects the replacement itself. The number of balls required to maintain the light for any time are placed on a wire passing through the focus of the reflector; the ball in the focus drops the moment it is sufficiently worn, and its place

is instantly taken by another-the next above it on the wire which two minutes before has fallen into a position to be gradually heated for doing duty in the focus.*

From a letter dated January 16, 1830, written to his sister, it appears that the Duke of Clarence, who a few months later became King William IV., had been expected to witness the experiments in his character of Master of the Trinity Corporation; and that an experiment which had been made with the lime-light, before the apparatus had been brought into perfect working order, had resulted in an explosion. Miss Drummond had cautioned her brother not to enter upon the experiments till he had completed his preparations.

"LONDON, January 16, 1830. "MY DEAR ELIZA,-A week, more than a week, has passed since I ought, and since I intended, to have answered your kind, kind letter; but every day and every evening has brought such constant occupation that I positively have not had time.

"The consequence, no doubt, has been many conjectures, and much exercise to my dear mother, if the bell rang about posttime. Now, what have been your conjectures? Another explosion, perhaps, and the heir-presumptive, along with all my beautiful apparatus, sent to the upper, or perhaps the under regions; or everything gone off well, and the Duke extremely

cases.

* This description is an abridgment from Mr Drummond's paper in the " Philosophical Transactions." There is an alternative contrivance for maintaining the constancy of the light in certain "Wherever the light is required to be diffused equally around, the renewal of the lime may be effected still more easily, by using a cylinder instead of a ball, which being gradually raised while revolving, brings fresh portions in succession opposite the jets. In a reflector a cylinder occasions partial shadows at the top and bottom; still, however, the simplicity and certainty with which it may be renewed, will probably entitle it to a preference even in this case." -Phil. Trans. 1830, p. 388.

delighted, expressed himself highly gratified, and intended conferring upon me some signal mark of his royal approbation! Well, to keep you in suspense no longer. The Duke was not present; he was unwell, and unable to leave his house. We were all prepared, for the messenger did not arrive till the last moment. The next Board day, when he is expected, is the 5th February. Meanwhile we proceed with the experiments, and it is with them that I have been so much engaged this week. But this is Saturday evening, an evening of repose and enjoyment, and I have taken advantage of it to discharge my debt to you. I was grieved to hear of more colds and plaisters, and I fear much that this fierce weather does not agree with you. . . Do you ride? How is the pony? Has John recovered, and has he been laying down the law? I think you might manage among you to write a little oftener. There are some long gaps in our correspondence, and some long intervals during which I hear nothing of you. Almost all my acquaintances have been ill more or less. I have great reason to be thankful that I have kept so well; indeed, notwithstanding all my work, I am in rude health, sleep but one sleep, and no palpitation. All the advice you gave me in your letter I acknowledge to be excellent, yet the exhibition was unavoidable, and so was the explosion. But I think they

have got over it; if not, I will tell them the first time I have an opportunity of making a speech, that if I had been making an experiment before men unacquainted with the peculiar nature of such experiments, I should have declined proceeding under such circumstances; but before enlightened and intelligent men, whose indulgence and partiality I had more than once experienced, I could have no hesitation in trying even a first experiment, deeming it the best compliment I could pay them to show them the apparatus under the most disadvantageous circumstances. My best and kindest love to you all at home. Adieu, my dearest Eliza, and believe me your ever affectionate brother, T. DRUMMOND."

The Duke of Clarence was present, and highly gratified, when the lights were exhibited at the Trinity House on the 5th of March; after the exhibition he