[TORRICELLI, Evangelista (1608-1647)]. [Carlo DATI (1619-1676), pseudonym, "Timauro Antiate"]. Lettera a Filaleti di Timauro Antiate della vera storia della cicloide, e della famosissima esperienza dell'argento vivo. Florence: all'Insegna della Stella, 1663.
4o (222 x 160 mm). Collation: A-B4 C6. 14 leaves. Drop-title. 3 small woodcut illustrations. (Light foxing.)19th-century half calf, spine panelled in gilt and blindstamped.
EXTREMELY RARE FIRST EDITION OF TORRICELLI'S DESCRIPTION OF HIS EXPERIMENTAL PROOF OF BAROMETRIC PRESSURE. Torricelli had described his experiment and his interpretation of it in a letter to Michelangelo Ricci dated 11 June 1644. Nearly 20 years later, the philologist Carlo Dati published in this short pamphlet important extracts from Torricelli's correspondence, including the letter to Ricci, Ricci's reply, and Torricelli's answer of 28 June 1644. A list of Torricelli's manuscript letters and notes, with their locations at the time, is printed at the end.
Torricelli is best known for his discovery that liquids are pushed up in a tube by the pressure of the atmosphere on the surface outside the tube. Galileo had shown experimentally the weight of atmospheric air in 1613, but had failed to recognize the source of the suction phenomena as the weight of the air, instead invoking a "force of vacuum". Torricelli, who conducted his experiments with progressively heavier liquids, culminating in mercury, both clearly proved and correctly interpreted the existence of atmospheric pressure. Although Torricelli'e early death prevented him from completing his experiments, he had stated in his first letter his hope to devise a means to measure the density of the air, and he is credited with the invention of the mercury barometer in theory, if not in practice. Copies of Torricelli's two letters to Ricci circulated in manuscript among Italian scientists, but the real disseminator of the news was the Pre Marin Mersenne, who obtained copies of the letters from Peiresc. On a trip to Italy, Mersenne had Torricelli demonstrate the experiment again. "On his return to France, he informed his friends of Torricelli's experiment, giving rise to flourishing experimental and theoretical activity. Discovery of the barometer, Vincenzio Antinori wrote, changed the appearance of physics just as the telescope changed that of astronomy, the circulation of the blood, that of medicine, and Volta's pile, that of molecular physics" (DSB). PMM 145; Norman 2087.