locks
depends on the doctrine of combinations, or multiplication of numbers
into each other, which is known to increase in the most rapid
proportion. Thus, a lock of five slides admits of 3,000 variations,
while one of eight will have no less than 1,935,360 changes; in other
words, that number of attempts at making a key, or at picking it, may
be made before it can be opened.

[2] The weight raised by a single press at the Britannia Bridge was
1144 tons.

[3] Dr. Thomas Young, in his article on Bramah in the Encyclopaedia
Britannica, describes the "rotative principle" as consisting in making
the part which acts immediately on the water in the form of a slider,
"sweeping round a cylindrical cavity, and kept in its place by means of
an eccentric groove; a contrivance which was probably Bramah's own
invention, but which had been before described, in a form nearly
similar, by Ramelli, Canalleri, Amontons, Prince Rupert, and Dr. Hooke.

[4] A Letter to the Right Hon. Sir James Eyre, Lord Chief Justice of
the Common Pleas, on the subject of the cause Boulton and Watt v.
Hornblower and Maberly, for Infringement on Mr. Watt's Patent for an
Improvement of the Steam Engine. By Joseph Bramah, Engineer. London,
1797.

[5] Sir Samuel Bentham and Marc Isambard Brunel subsequently
distinguished themselves by the invention of wood-working machinery,
full accounts of which will be found in the Memoirs of the former by
Lady Bentham, and in the Life of the latter by Mr. Beamish.

[6] "Record of the International Exhibition, 1862." Practical
Mechanic's Journal, 293.

[7] In this, as in other methods of employing power, the moderns had
been anticipated by the ancients; and though hydraulic machinery is a
comparatively recent invention in England, it had long been in use
abroad. Thus we find in Dr. Bright's Travels in Lower Hungary a full
description of the powerful hydraulic machinery invented by M. Holl,
Chief Engineer of the Imperial Mines, which had been in use since the
year 1749, in pumping water from a depth of 1800 feet, from the silver
and gold mines of Schemnitz and Kremnitz. A head of water was
collected by forming a reservoir along the mountain side, from which it
was conducted through water-tight cast-iron pipes erected
perpendicularly in the mine-shaft. About forty-five fathoms down, the
water descending through the pipe was forced by the weight of the
column above it into the bottom of a perpendicular cylinder,