fect working order, an explosion took place. Drummond's sister, on hearing of the accident, wrote warning him to be more careful in future. He replied playfully :

"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 post-time. Now, what have been your conjectures? Another explosion, perhaps, and the heir-presumptive,1 along with all my beautiful apparatus, sent to the upper, or perhaps the under regions; or everything gone off well, and the Duke extremely 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 plasters, and I fear much that this fierce weather does not agree with you. . . . "Do you ride?

How is the pony?

Has John re

1 The Duke of Clarence, afterwards William IV., who, in his character of Master of the Trinity Corporation, was expected to witness the experiments. -McLennan.

covered, 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 been 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 affectionate brother,

"T. DRUMMOND."

In May 1830 the light was exhibited at the temporary lighthouse, Purfleet, and we have a graphic account of the experiment from Captain Basil Hall, R.N., in a letter to Drummond. Captain Hall witnessed the exhibition from the Trinity Wharf, Blackwall, a distance of 10 miles from Purfleet; and among the observers with him were Sir George Cockburn and Mr Barrow from the Admiralty, the Lord Advocate of Scotland, Sir Thomas Brisbane, Colonel Colby, Captain Beaufort, hydrographer to the Admiralty. Captain Hall wrote:

CAPTAIN BASIL HALL TO DRUMMOND.

"ST JAMES'S PLACE, June 1, 1830.

"MY DEAR SIR,-You wished me to take particular notice of last night's experiments with the different kinds of lights exhibited at Purfleet, and observed at the Trinity Wharf, Blackwall; but I have little to add to what I told you respecting those on the evening of the 25th instant; indeed, it is not within the compass of language to describe accurately the details of such experiments, for it is by ocular evidence alone that their merits can be understood.

Essentially, the experiments of last evening were the same as those of the 25th, and their effects likewise. The degrees of darkness in the evenings, however, were so different, that some particular results were not the same. The moon last night being nine or ten days old, lighted up the clouds so much, that even when the moon herself was hid, there was light enough to overpower any shed upon the spot where we stood by your distant illumination; whereas on the 25th, when the night was much darker, the light cast from the temporary lighthouse at Purfleet, in which your apparatus was fixed, was so great, that a distinct shadow was thrown upon the wall by any object interposed. Not the slightest trace of any such shadow, however, could be perceived when your light was extinguished and any of the other lights were exposed in its place.

"In like manner on the evening of the 25th, it was remarked by all the party at the Trinity Wharf, that, in whatever direction your light was turned, an immense coma or tail of rays, similar to that produced by a beam of sunlight in a dusty room, but extending several miles in length, was seen to stream off from the spot where we knew the light to be placed, although, owing to the reflector being turned too much on one side, the light itself was not visible.