Penny BlackThe Penny Black was the world's first adhesive postage stamp used in a public postal system. It was first issued in the United Kingdom on 1 May 1840 but was not valid for use until 6 May. The stamp features a profile of Queen Victoria. In 1837, British postal rates were high, complex and anomalous. To simplify matters, Sir Rowland Hill proposed an adhesive stamp to indicate pre-payment of postage. At the time it was normal for the recipient to pay postage on delivery, charged by the sheet and on distance travelled.
Sun and planet gearThe sun and planet gear is a method of converting reciprocating motion to rotary motion and was used in the first rotative beam engines. It was invented by the Scottish engineer William Murdoch, an employee of Boulton and Watt, but was patented by James Watt in October 1781. It was invented to bypass the patent on the crank, already held by James Pickard. It played an important part in the development of devices for rotation in the Industrial Revolution.
HighwaymanA highwayman was a robber who stole from travellers. This type of thief usually travelled and robbed by horse as compared to a footpad who travelled and robbed on foot; mounted highwaymen were widely considered to be socially superior to footpads. Such criminals operated until the mid- or late 19th century. Highwaywomen, such as Katherine Ferrers, were said to also exist, often dressing as men, especially in fiction. The first attestation of the word highwayman is from 1617.
Diminishing returnsIn economics, diminishing returns are the decrease in marginal (incremental) output of a production process as the amount of a single factor of production is incrementally increased, holding all other factors of production equal (ceteris paribus). The law of diminishing returns (also known as the law of diminishing marginal productivity) states that in productive processes, increasing a factor of production by one unit, while holding all other production factors constant, will at some point return a lower unit of output per incremental unit of input.
