Mr. Johnston was the son of the Rev. John Johnston, minister of Arngask, and brother-gerrnan to Dr. Johnston, of North Leith. He carried on business for many years as a private banker, in company with Mr. Donald Smith, under the firm of Johnston & Smith. This concern, however, proved unfortunate, having met with a series of losses—among the first of which was a robbery to a considerable amount. The particulars of this affair are fully given in the following advertisements from the Courant of 1768 :—

"On Friday evening last [the 12th August] the lock of the outer door of the compting-house of Johnston & Smith, bankers in the Exchange, was opened by some wicked persons, as supposed by a counterfeit key, and eight hundred pounds sterling stolen out of their drawers, in the following Bank notes, viz.:—

Of the Royal, and Bank of Scotland, - £194 9 0
British Linen Company, - - - - 362 2 0
Dumfries Notes,.....126 0 0
Glasgow Notes,.....64 10 0
General Bank of Perth, - - - - 32 0 0
Dundee Notes (Jobson's), - - - 40 0 0
Several small Notes and Silver, - - 11 1 0
£830 2 0

It is entreated that every honest person will give the Magistrates of Edinburgh, or Johnston & Smith, notice of any circumstances that may fall under their observation for discovering the offenders; and farther, the said Johnston & Smith will give the informer a reward of Five Pounds sterling for every hundred pounds sterling that shall be recovered in consequence of such information. As some smith may very innocently have made a key from an impression of clay or wax, such smith giving information, as above, so as the person who got the key may be discovered, shall be handsomely rewarded."

"BY ORDER OF THE HONOURABLE THE MAGISTRATES OF EDINBURGH.

"Whereas, on Sunday night last, the 14th inst., there was laid down or dropped at the door of the Council Chamber of this City, the sum of two hundred and twenty-five pounds sterling, in bank notes, wrapped in a piece of grey paper, which was found by Robert Burton, a porter, and immediately after delivered by him to one of the Magistrates : This is to give notice, that the above sum is now sealed up, and in the hands of the City Clerks, and will be delivered to any person who shall prove the property thereof, with deduction of a reasonable allowance to the porter who found it."

The notes were proved to be the property of Messrs. Johnston & Smith. In addition to the reward, a proclamation was issued by the King, promising a free pardon to any one, except the principal, concerned in the robbery, who should make a disclosure ; and, as a further inducement, fifty guineas additional were offered by Johnston & Smith to the informer. These measures were ineffectual; and no traces of the delinquent could be found, till the apprehension of Deacon Brodie, twenty years afterwards, induced strong suspicion that he was concerned in it. It was then recollected that, prior to the robbery, the Deacon had been employed in making various repairs on the premises of Johnston & Smith, and had occasion to be frequently in the bank. The key of the outer door, from which it was ascertained he had taken an impression in putty, usually hung in the passage, which was rather dark and narrow. The premises are now occupied by Mr. Adam Luke, treasurer to Heriot's Hospital.

Not long after this affair, the firm experienced some severe reverses, arising from a sudden depression in trade, besides losing a box containing one thousand guineas, which fell into the sea at Leith, while being handed from a boat to the ship in which it was to be forwarded to Loudon. Immediately after this accident the firm stopped payment, and compounded with their creditors at the rate of fifteen shillings in the pound. Various attempts were made to recover the box. Among others who dived for the treasure was a tailor in Leith, somewhat famous for his aquatic dexterity. All his exertions, however, although repeated with great perseverance for some time, proved unsuccessful.

The copartnery was now broken up; after which Mr. Smith commenced business on his own account, as a private banker; and, during the remainder of a long life, was highly successful and respected, aud filled the office of Lord Provost in the years 1807 and 1808. Mr. Smith married Miss Palmer, daughter of an eminent cabinet maker in Chapel Street, by whom he obtained considerable property. He died at his house in West Nicolson Street, in 1814, aged seventy-five. His son, the late Alexander Smith, Esq., who carried on the banking business, met with a tragical fate, having been killed in the spring of 1833, by the falling in of a floor of a house in Picardy Place, during the sale of the collection of pictures belonging to the late John Clerk of Eldin, Esq., one of the Senators of the College of Justice. Mr. Johnston also continued, for several years, to discount bills in a small way, until a Mr. John Alston, hardware and toy merchant (merchant in Scotland at that time was applied to all traders, whether wholesale or retail). having failed, he took the bankrupt's goods at a valuation, and entered into his shop as his successor. In the course of a short time he added groceries to his other stock; and, finding that branch turn out the most advantageous, latterly discarded the hardware business altogether.