<P> The invention of the vacuum pump paved the way for the experiments of Robert Boyle and Robert Hooke into the nature of vacuum and atmospheric pressure . The first such device was made by Otto von Guericke in 1654 . It consisted of a piston and an air gun cylinder with flaps that could suck the air from any vessel that it was connected to . In 1657, he pumped the air out of two conjoined hemispheres and demonstrated that a team of sixteen horses were incapable of pulling it apart . The air pump construction was greatly improved by Robert Hooke in 1658 . </P> <P> Evangelista Torricelli (1607--1647) was best known for his invention of the mercury barometer . The motivation for the invention was to improve on the suction pumps that were used to raise water out of the mines . Torricelli constructed a sealed tube filled with mercury, set vertically into a basin of the same substance . The column of mercury fell downwards, leaving a Torricellian vacuum above . </P> <P> Surviving instruments from this period, tend to be made of durable metals such as brass, gold, or steel, although examples such as telescopes made of wood, pasteboard, or with leather components exist . Those instruments that exist in collections today tend to be robust examples, made by skilled craftspeople for and at the expense of wealthy patrons . These may have been commissioned as displays of wealth . In addition, the instruments preserved in collections may not have received heavy use in scientific work; instruments that had visibly received heavy use were typically destroyed, deemed unfit for display, or excluded from collections altogether . It is also postulated that the scientific instruments preserved in many collections were chosen because they were more appealing to collectors, by virtue of being more ornate, more portable, or made with higher - grade materials . </P> <P> Intact air pumps are particularly rare . The pump at right included a glass sphere to permit demonstrations inside the vacuum chamber, a common use . The base was wooden, and the cylindrical pump was brass . Other vacuum chambers that survived were made of brass hemispheres . </P>

Why did so many great minds emerge at the same time during the scientific revolution