De Furtivis Liter arum Notis

SUBJECT AREA: Steam and internal combustion engines

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Giambattista della Porta spent most of his life in Naples, where some time before 1580 he established the Accademia dei Segreti, which met at his house. In 1611 he was enrolled among the Oziosi in Naples, then the most renowned literary academy. He was examined by the Inquisition, which, although he had become a lay brother of the Jesuits by 1585, banned all further publication of his books between 1592 and 1598.

His first book, the Magiae Naturalis, which covered the secrets of nature, was published in 1558. He had been collecting material for it since the age of 15 and he saw that science should not merely represent theory and contemplation but must arrive at practical and experimental expression. In this work he described the hardening of files and pieces of armour on quite a large scale, and it included the best sixteenth-century description of heat treatment for hardening steel. In the 1589 edition of this work he covered ways of improving vision at a distance with concave and convex lenses; although he may have constructed a compound microscope, the history of this instrument effectively begins with Galileo. His theoretical and practical work on lenses paved the way for the telescope and he also explored the properties of parabolic mirrors.

In 1563 he published a treatise on cryptography, De Furtivis Liter arum Notis, which he followed in 1566 with another on memory and mnemonic devices, Arte del Ricordare. In 1584 and 1585 he published treatises on horticulture and agriculture based on careful study and practice; in 1586 he published De Humana Physiognomonia, on human physiognomy, and in 1588 a treatise on the physiognomy of plants. In 1593 he published his De Refractione but, probably because of the ban by the Inquisition, no more were produced until the Spiritali in 1601 and his translation of Ptolemy's Almagest in 1605. In 1608 two new works appeared: a short treatise on military fortifications; and the De Distillatione. There was an important work on meteorology in 1610. In 1601 he described a device similar to Hero's mechanisms which opened temple doors, only Porta used steam pressure instead of air to force the water out of its box or container, up a pipe to where it emptied out into a higher container. Under the lower box there was a small steam boiler heated by a fire. He may also have been the first person to realize that condensed steam would form a vacuum, for there is a description of another piece of apparatus where water is drawn up into a container at the top of a long pipe. The container was first filled with steam so that, when cooled, a vacuum would be formed and water drawn up into it. These are the principles on which Thomas Savery's later steam-engine worked.

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