M. Volta constructs and combines his apparatus in various ways and forms, more or less powerful, convenient or amusing. One is as follows (Fig. 1, pl. 13,), which he calls a _couronne de tasses_. He disposes in a row a number of cups of wood, or earth, or glass, or any thing but metal, half filled with pure water, or salt water or lye; these are all made to communicate in a kind of chain, by several metallic arcs of which one arm or link, Aa, or only the extremity A, immersed in one of the cups, is of copper, or of copper silvered, and the other Z, immersed in the following cup, is of tin, or rather of zinc, the other two being soldered together near the crown of the arch. It is evident that a series of these cups, thus connected together, either in a straight or curved line, by the two metals and the intermediate liquid, is similar to the pillar or pile before described, and consequently will exhibit similar effects. Thus, to produce commotion or sensation in the hands and arms, we need only dip one hand into one of the cups and the finger of the other hand into another cup, sufficiently far from the former; and the action will be so much the stronger as the two cups are farther asunder, or have the more intermediate cups; and consequently the greatest by touching the first and the last in the chain. * * * * * M. Volta concludes with various remarks and cautions in using this instrument; showing that it is perpetual in its virtue, renewing its charge spontaneously, and serving most of the purposes of the ordinary electrical machines, and even affecting and manifesting its power by most of the human senses, viz. feeling, tasting, hearing, and seeing. FOOTNOTES: [Footnote 20: From the _Transactions of the Royal Society of London_.] XIX PIERRE SIMON LAPLACE 1749-1827 _Pierre Simon Laplace, born at Beaumont-en-Auge, Normandy, March 28, 1749, became a teacher of mathematics at Beaufort before he was eighteen years old. He gained d’Alembert’s attention by a letter which he wrote to him on the principles of mathematics. After 1770 he engaged with Lagrange in determining the permanency of the solar system by studying its perturbations and interactions, and finally suggested how these changes were periodic. His monumental work, in five volumes, “Mechanics of the Heavens” (1799-1825), gave a comprehensive description of the movements of the solar system, and his “System of the World” proposed the nebular theory of the origin of the universe. His researches were important in the development of modern astronomy because he substituted a dynamic for the descriptive point of view. He died at Arcueil, March 5, 1827._ THE NEBULAR HYPOTHESIS[21]