1643. 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. Materials, construction, and aesthetics 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. 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. Instrument makers of the late 17th and early 18th centuries were commissioned by organizations seeking help with navigation, surveying, warfare, and astronomical observation. The increase in uses for such instruments, and their widespread use in global exploration and conflict, created a need for new methods of manufacture and repair, which would be met by the Industrial Revolution. Criticism The idea that modern science took place as a kind of revolution has been debated among historians. A weakness of the idea of a scientific revolution is the lack of a systematic approach to the question of knowledge in the period comprehended between the 14th and 17th centuries, leading to misunderstandings on the value and role of modern authors. From this standpoint, the continuity thesis is the hypothesis that there was no radical discontinuity between the intellectual development of the Middle Ages and the developments in the Renaissance and early modern period and has been deeply and widely documented by the works of scholars like Pierre Duhem, John Hermann