Tool of science and stethoscope of the engineer: important steam engine indicators of the 19th century

Professor Paul Zoller

The steam engine’s development into an economical and reliable source of almost unlimited power was the greatest technological achievement of the 19th century. In this development, a little instrument called the steam-engine indicator played a very significant role. An engine indicator simply provides a written record of cylinder pressure vs. stroke of an engine. Without interrupting normal work, this simple record enabled engineers to measure power, and routinely check the proper operation of engines in the factory, on the railways, and at sea, assuring continuous economical and reliable performance. Moreover, cards taken during extensive engine trials provided the scientific and engineering information necessary to improve engine practice, often based on (and contributing to) the new mechanical theory of heat (thermodynamics). Two dozen makers in England, France, the United States and Germany made ingenious improvements to the indicator throughout the 19th century, manufacturing several ten thousand accurate, reliable, and beautifully made instruments that could deal with the ever higher pressures and engine speeds reached during the period. The dominant American contributions, which began in 1862, are especially significant as early manifestations of Yankee ingenuity. We will trace the development of the indicator and its application from Watt’s first attempts very late in the 18th century to the end of the 19th century, trough instruments invented, improved, or made by Field, McNaught, Hirn, Richards, Elliott Brothers, Thompson, Crosby, and others.

Morse’s telegraphic indicator and the electro-chronograph

Professor Rand B. Evans

The ‘American method’ of determining longitude was born of the union of an astronomical clock that produced a timed pulse, telegraphy, the reading of a star transit and graphic recording of the observer’s response to the transit. The American method reduced the human error considerably over the ‘eye and ear’ method of Bradley and Maskelyne. Three Americans are credited with the creation of the electro-chronograph essential for the graphic recording. What has been missed in this controversy on credit for the electro-chronograph is that the device used in virtually all these early observations, the Morse telegraphic register, was not only prior to these devices but was the basis for the drum-type electro-chronograph. It continued in use parallel to the various versions of electro-chronographs well into the 1880s. This talk will show how Locke’s electro-chronograph developed from the Morse register and how the register continued to play a role in the determination of longitude.

Between purity and danger: testing milk for penicillin with the Delvotest

Dr Robert Bud

The Delvotest detector of penicillin milk was introduced in the early 1970s. It provided the farmer with a convenient way of protecting the individual consumer and the cheese producer from a dangerous pollutant that could occasionally kill people or destroy a batch of cheese. Of course, this conception of penicillin was an ironic inversion of its other image as a miracle drug. The Delvotest was itself a descendant of Fleming’s original Petri dish with which he first explored medicine’s greatest cure. Like Fleming’s original apparatus it worked by inhibiting bacterial growth. Now however it was being used to separate good penicillin in the right place from dangerous penicillin in the wrong place. Historians of scientific instruments have paid little attention to the meaning of such devices, however their capacities determine the definition of pollution, and the limits of legislation as well as the sense of safety felt by citizens.