But there are many other names which we should not easily guess to come from the names of inventors. People talk of a macadamized road without knowing that these roads are so called because they are made in the way invented by John M'Adam, who lived from 1756 to 1836. The name _macadam_ is often used now to denote the material used in making roads. Sometimes this material is of a sort which John M'Adam would not have approved of at all, for he did not believe in pouring a fluid material over the stones, or in the heavy rollers which are now often used in making new roads. Another useful article, the homely _mackintosh_, takes its name from that of another Scotsman, Charles Macintosh, who lived at the same time as M'Adam. It was he who first, in 1823, finished the invention of a waterproof cloth. In the eighteenth and nineteenth centuries many great discoveries were made in science, and many names of discoverers and inventors have been preserved in scientific words. _Galvanism_, one branch of electricity, took its name from Luigi Galvani, an Italian professor, who made great discoveries about electricity in the bodies of animals. Every one has heard of a galvanic battery, but not everybody knows how it got its name. _Mesmerism_, or the science by which the human mind is influenced by suggestions from itself or another mind, took its name from Friedrich Anton Mesmer, who first made great discoveries about animal magnetism. Another famous discoverer of the powers of electricity, and one who is still a young man, is Guglielmo Marconi, a native of Bologna. It was he who invented the great system of wireless telegraphy which is now used in nearly all big ships. In 1899 he first succeeded in sending a message in this way from England to France, and in the next year he sent one right across the Atlantic. Now ships frequently send a _Marconigram_ home when they are right in the middle of the ocean; and many lives have been saved through ships in distress having been able to send out wireless messages which have brought other vessels steaming up to their aid. In fact, this invention of Marconi's is, perhaps, the greatest of all modern inventions, and it is but right that it should preserve his name. A different kind of invention has preserved the name of the fourth Earl of Sandwich, an eighteenth-century nobleman, who was so fond of card games that he could not bear to leave the card table even to eat his meals, and so invented what has ever since been called by his name--the _sandwich_. Not unlike the origin of the name sandwich is that of _Abernethy_ biscuits, so called after the doctor who invented the recipe for making them.