Projecting the Wonder of Life

Expert microscopists and instrument makers like George Adams Sr. and Johann Nathanael Lieberkühn presided over the public's fascination with microscopes and the worlds they revealed. Frogs proved useful in technological and biological appeals to the public's sense of wonder, and experts developed technological and rhetorical tools to manage those public perceptions.

Early hygrometers used hair, whalebone or catgut - materials that stretch when subjected to humidity - to gauge the dampness of air. The rate of water evaporation from a wet surface is another way of determining the quantity of water vapour in the surrounding atmosphere. Humidity plays a large role in how we 'feel' temperature.

Early studies of dew point

Studied since the fifteenth century, dew-point is the temperature at which moisture in the air condenses as liquid. An investigation into this phenomena by the Grand Duke of Tuscany, Ferdinand II (1610-1670), led to the construction of a condensation hygrometer.

He noticed that during the hot summer months water formed on the outside of an iced glass depending on the temperature and wind. Curious about the nature of the atmosphere and the conditions that changed water vapour into liquid, Ferdinand II invented his instrument. Consisting of a cone-shaped vessel filled with ice, Ferdinand's crude hygrometer enabled him to conduct experiments on how temperature and air circulation affected water vapour in our atmosphere and the conditions that produced dew.

In 1751, Charles le Roy (1723-1789) attempted to chart dew-point by pouring cold water into a glass container, observing the formation of condensation and then measuring the water's temperature. The water was then decanted into a second glass and the process repeated.

'Red sky at night, shepherd's delight. Red sky in morning, shepherd's warning.' By the end of the eighteenth century, weather lore remained a dominant form of weather prediction. Based on the reading of natural signs, such as the behaviour of animals or the appearance of the sky, weather-wise expressions commonly circulated as a type of forecasting. Nineteenth-century meteorology saw the development of weather forecasting based on measurable phenomena, such as wind, the intensity of the Sun and, in many cases, the character and appearance of clouds.

In 1746, Adams released a guide to the use of his own products entitled Micrographia Illustrata, a copy of which we hold in the Whipple Collection. It includes several prints representing the frog-plate's use (Image 1 and 2). Adams' prints gruesomely depict the ensemble of hooks and wires that strip apart and isolate the layers of the frog's skin.

Instrument makers like Adams navigated shifting social divisions by publishing catalogues that doubled as philosophical treatises. Adams' Micrographia Illustrata serves as an advertisement for his wares, an instruction manual for their use, an illustration of the truths they reveal, and a theological defence of their propriety. Publishing was one of many ways that scientists and instrument makers could communicate with the public and advertise their products.

Adams claimed that many of his micrographic illustrations were produced by tracing an image cast through a solar microscope, which could project microscopic images onto a screen. One example is seen here (Image 2): the frog's skin has been peeled back, and a vivid image of its circulating blood is projected onto a screen. There, the image's outlines are traced and then rendered into a copperplate engraving for inclusion in Adams' book. His describes the majestic beauty of the image produced by this instrumental ensemble: when arranged with Adams' skill, "no words can describe the wonderful scene which will then be presented to your sight," he promised his readers. Frogs were Adams' organism of choice in such attempts to demonstrate both the visual wonders of the living body and the microscopes that reveal it.

Read more:

• For more about public displays of microscopy, see Public Microscope Shows in the 18th Century.
• For more about the history of this ambiguous but powerful boundary between scientists and craftsmen, see Ziegler's Frog Embryos.
• For more about frogs' importance to later instrument makers, see Frogs and Physiological Instruments in 20th Century Cambridge.