"Now, last night there was none of this singular appearance visible; but whether this was caused by the presence of the moonlight, or by the absence of the haze and drizzling rain which fell during the evening of the 25th, I cannot say. I had hoped that the appearance alluded to was to prove a constant accompaniment to your light, in which case it might, perhaps, have been turned to account for the purposes of lighthouses. If in hazy or foggy weather this curious effect of reflected light from the atmosphere be constant, it may help to point out the position of lighthouses, even when the distance of the observer is so great that the curvature of the earth shall render it impossible for him to see the light itself.

"The following experiments, tried last night, were the same as those of the 25th, and certainly no comparative trials could be more fairly arranged :—

"EXP. I. The first light exposed was the single Argand burner with a reflector. This was quite distinctly seen, and all the party admitted it to be a good light. After several minutes, this was put out.

"EXP. II. The seven Argand burners were next shown, each in its reflector; and this was manifestly superior to the first, but how much so I cannot say-perhaps four times as conspicuous. Both these lights had an obvious tinge of brown or orange.

"EXP. III. The third light which was exposed (on the seven Argands being put out) was that behind the French lens; and I think it was generally admitted by the party present that this light was whiter and more intense than that from the seven Argands, though the size appeared very much the same.

"EXP. IV. The fourth light was that which you have devised, and which, instead of the clumsy word "lime," ought to bear the name of its discoverer. The Drummond light, then, the instant it was uncovered, elicited a sort of

shout of admiration from the whole party, as being something much more brilliant than we had looked for. The light was not only more vivid and conspicuous, but was peculiarly remarkable from its exquisite whiteness. Indeed, there seems no great presumption in comparing its splendour to that of the sun; for I am not sure that the eye would be able to look at a disc of such light, if its diameter were made to subtend half a degree.

"The next series of experiments was the most interesting and decisive of all. Each of the lights above enumerated, viz., the single Argand burner, the seven Argands, and the French lens, were exposed, one at a time, in company with your light, in order to try their relative brilliancy.

"First Comparative Experiment.-The single Argand burner was first exposed to this comparative ordeal, and nothing could be more pitiable than the figure it cut. Many of the party could not see the Argand light at all; while others could just detect it 'away in a corner,' as some one described it. It was also of a dusky orange tinge, while your light was of the most intense whiteness.

"Second Comparative Experiment. The seven Argand burners were now substituted in place of the single light. All the party could now see both lights, but the superiority. was not much less obvious. I really cannot affix a proportion either as to size or brilliancy; but I should not hesitate to say that your light was at least six or eight times as conspicuous; while in brilliancy or purity, or intensity of light (for I know not precisely what word to use to describe the extreme whiteness), the superiority was even more remarkable. All this which I have been describing was expressed, and appeared to be quite as strongly felt, by the rest of the company, to the number, I should suppose, of five-and-twenty or thirty persons, who were all closely on the watch.

"Third Comparative Experiment.-The next compara

tive trial was between the French lens and your light. The superiority here was equally undeniable, though the difference in the degree of whiteness was not so remarkable. The French light, however, is so nearly similar to that from the seven Argands, that the comparison of each of them with your light gave nearly the same results, and all equally satisfactory on the score of your discovery.

"Final Experiment.-The flashes with which the experiments concluded were very striking, and might, I think, be turned to great account in rendering lighthouses distinct from one another. The revolutions were not effective, and, as I said before, there was no appearance last night of those enormous comets' tails which swept the horizon on the night of the 25th, to the wonder of all who beheld them: neither could there be detected the slightest trace of any shadow from the light thrown towards us; and I suspect none will ever be seen, when the moon, whether the night be clouded or not, is of so great a magnitude.

"Such is the best account I can give of what we witnessed; and I need only add, that there seemed to be amongst the company but one opinion of the immense superiority of your light over all the others brought into comparison with it.-I am, &c., "BASIL HALL."

Up to the spring of 1831 Drummond continued engaged in trying experiments and improving the invention. The brilliancy of the light was established beyond all doubt, and the only question which remained, as to its suitability for lighthouse purposes, was one of expense. The result of his labours and the experiments he gives in a letter to his mother, dated January 22, 1831. He writes :

"Truly this same light gives no small trouble. . . . In the last paper which I sent to the Commissioners, I stated

that the French light equals, if it does not surpass, the best of the lights in our lighthouses in splendour; while it is superior to them in economy and facility of management. This Stevenson either denies, or has hitherto been negligent in ascertaining. . . . The experiments at Inchkeith have been ordered by the Commissioners (of the Northern Lights), with a view to judge of the point themselves, and not trust to Stevenson's opinion. It is a question between the present method and the French light, not between mine and either. Their relative values have been ascertained by the Trinity House and Blackwall experiments, in a way which admits of no doubt. To recommence similar experiments would be mere trifling. There are obstacles in my way of a different kind, relating to the manufacture of the gas, management, &c., which I am now endeavouring to remove. With respect to brilliancy there can be no doubt."

About this time a copy of Drummond's paper on lighthouses, which had been read before the Royal Society, was presented to the King, William IV. We have an interesting account of this incident in a pleasant letter from Drummond to his mother.

DRUMMOND TO HIS MOTHER.

January 24, 1831.

"MY DEAR MOTHER,-I have begun with a sheet as long as your own, but whether I shall fill it as well is another question. The business part of your letter shall be first answered, and the remainder of the sheet devoted to amuse you.

"Now, as you sent me a description of the lecture. [most probably a lecture delivered in Edinburgh on the Drummond light], I mean to send you a description of another scene which may not gratify you so much, but which, I hope, will nevertheless interest you. Believe me,

my dear Mother, the chief, perhaps the only pleasure which I received from the account of the lecture, arose from your being there to hear it; and if with you I mourn the absence of those, from sickness or from death, who would have participated in your feelings, still I am gratified that among those who did witness it, my dearest Mother was one. Now to return to my promised description, for one forgets there are limits to a sheet of paper.

"Among others to whom it was considered proper that a copy of my paper should be presented, was a certain illustrious personage called the King. Now, at the mention of this word away goes your imagination long before my description, and you conclude at once that I am on the high road to honour, rewards, emoluments, and so forth. Not so, however; yet have I had honour to a certain extent-as much as could with propriety be bestowed, and more than was expected. Well, then, the reason for presenting the paper to the King was, that his Majesty is still Master of the Trinity House, and had, as Duke of Clarence, been present at many of the experiments. It was necessary to obtain the King's permission to present the book in question, which he was graciously pleased to give to the Deputy-Master, Captain Woolmore, his old friend. Next came the question, how it was to be presented. I had intended sending a copy in its blue cover to Mr Woolmore for this purpose, but I was given to understand that that would not be according to etiquette; and it was finally resolved that the little pamphlet should be made into a little book, bound in morocco, and stamped with the royal arms; and furthermore, that I should accompany Captain Woolmore to Brighton, when he went to present the monthly report of the Trinity House to the King as Master.

"This being settled, another difficulty arose about uniform. Our uniform has been lately changed; it was