The conclusion at which he arrived was that, whilst the colours followed the laws of chance as they are generally understood, the other even chances, _passe_ and _manque_, _pair_ and _impair_, exhibited such capriciousness in their recurrence as could not have been expected had roulette been played continuously through the whole period of geological time. The roulette wheels of Monte Carlo are perfectly honest machines. The cylinder of each is sheet copper, carefully balanced and strengthened by bands of metal. It revolves in its bed on a vertical pivot of steel, the top of which has a cup-like hollow, into which oil is poured. A mechanic, whose business it is to clean and prepare the wheels every morning, pours oil also into the gun-metal socket which forms the centre of the wheel, and it is then dropped into its place upon the pivot. The great care which is taken by the authorities to ensure the absolute accuracy of their roulette wheels is based upon very sufficient grounds, for a slight defect in one of those machines once cost them a large sum. Amongst the frequenters of the rooms at Monte Carlo there is always a large number of astute and none too scrupulous individuals quick to note any little circumstance likely to be of advantage to themselves. For this reason some slight tendency of the roulette wheel to stop in such a way as to cause a certain group of numbers to have an advantage over the rest is very quickly noticed and advantage taken of it. A mechanic from Yorkshire, Jaggers by name, once cost the Casino some two million francs. Well aware of the difficulty of maintaining a nicely adjusted machine in a perfectly stable condition, Jaggers engaged six assistants, whom he posted at different tables to note the numbers at roulette all day long, whilst he himself undertook to make an elaborate analysis of the results. After a month's play peculiarities were clearly to be discovered in the appearance of the numbers at each of the tables quite out of consonance with the law of average, some numbers turning up more, some less. Having ascertained this fact Jaggers and his men began to play on the numbers which kept ahead of the rest, and won some hundred and forty thousand pounds. The authorities then realised that all was not right, and changed the roulette wheels from one table to another for every day's play, with the result that the bank recovered £40,000. Jaggers, however, was not yet defeated, for by searching observations he discovered minute marks on most of the six wheels, which enabled him to follow them from table to table--a mere scratch was enough. In a short time he and his assistants knew what numbers would be most likely to recur at certain tables, and the £40,000 which the bank had regained was soon won back.