Tyndall, John, 1820-1893 · New York, D. Appleton · leaf 94
ia-rubber (k, fig. 23), and, instead of thelarge lid, a plate of brass, e, 5 inches in diameter. Thisplate is attached by silk threads, like a scale pan, to oneend of a balance-beam (a b, fig. 23). It now rests uponthe unexcited india-rubber. I determine its weight, andfind it to be 100 grammes.… … To lift the lid, therefore, from the excited resin cake aquantity of work has to be done in excess of what isnecessary to overcome the mere force of gravity. Thespark of the electrophorus is the exact equivalent of thisexcess. By-and-by we will trace farther back the pedigreeof the spark. At…
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