On the afternoon of the day of the robbery, a murky fog, such as Londoners know so well and heartily dislike, hung over the metropolis. The street lamps afforded but a dull light in the thoroughfares; shops and offices were lighted up for the evening's business; and the afternoon's work in the Hatton Garden Post-office was at its height (the registered-letter bag, containing some forty registered letters, having just been deposited in an ordinary bag hanging from a peg in the office), when suddenly, and without apparent cause, the whole of the lights in the office went out, and the place was plunged in almost total darkness. Consternation took possession of the female clerks behind the counter, while young clerks and boys from warehouses and offices, conceiving the occasion to be one for noise and merriment, helped to increase the confusion by clamour and hubbub outside the counter. No long time elapsed before matches were obtained and tapers lit, when it was immediately discovered that the tap of the gas-meter in the basement had been turned off; but on the tap being turned on again, the jets in the office were relit, and the place resumed its wonted appearance. The young ladies in the office being now able to see around them, soon detected the absence of the bag, which had been left hanging on the peg, and which they knew had not yet been despatched by them. It did not take long to realise that the bag had vanished--in fact, had been stolen; and to this day the property contained in the lost registered letters has not been recovered, nor have the persons concerned in the theft been traced. It is believed that two or more individuals were engaged in the robbery, the supposition being that one person got down into the basement without attracting attention, and turned off the gas, while another, so soon as darkness supervened, got by some means within the counter, and, unobserved, took the bag from the peg--all concerned making good their escape in the midst of the stir and noise by which they were surrounded. The whole adventure bears the impress of having been carefully planned and cleverly executed, and there is little doubt that the robbery was carried out by men who were experts in their nefarious calling. The value of the articles contained in the forty registered letters was about £15,000; and as the scene of the robbery lay in the midst of diamond merchants and jewellers, it is not surprising that precious stones and jewellery were the principal contents of these letters. Besides watches, bracelets set with pearls and diamonds, ear-rings, rings, &c., the following articles were among the property stolen--viz., eight parcels of rough diamonds, 147 turquoises, a quantity of small emeralds, 6000 drilled sapphires, 2000 pairs of garnet bores, 240 pairs of sapphire bores, a quantity of sapphires weighing 695 carats, several rubies and sapphires weighing 546 carats, &c., &c.