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546 decree read, "assisted at meetings organized for purposes contrary to the institutions of the country." Quetelet was discommoded by the action of the Government, and did not conceal the fact. Houzeau continued, however, to take part privately in the work of the observatory for a few months, till he started on a tour in Germany, Switzerland, and France. Sojourning at Lyons from the following February till May, he occupied himself with the preparation of several works, among them two treatises on Meteorology, which appeared afterward in the Encyclopédie populaire. In May, 1850, he settled in Paris, where he resided for five years, devoting himself principally to study. He was an industrious taker of notes, which related, not to science alone, but to all branches of human activity, and embraced anecdotes and jokes. He assisted M. d'Abbadie, of the Institute, in arranging the scientific observations which he had made in Ethiopia. He interested himself much in optical telegraphy. In conjunction with his brother he made experiments at Paris and Mons to learn if the light of the flashing of powder at one place could be seen at the other. Of course, these experiments were not successful, for such lights could not be seen at so great a distance. Some time afterward communication by the electric cable between England and France was interrupted, and Houzeau proposed to the English Cable Company to use a system of optical signals. Experiments were determined upon between Dover and Calais, but were stopped by the order of the French Government, declaring that such work should be done only by agents of the state. They were undertaken again in England, where this kind of interference could not take place, between Southend and Whitstable. The first experiments were successful, but the populace, excited by so much night-work with fires, and fancying that the oyster crop would be damaged by them, mobbed the experimenters and stoned Houzeau's lodgings.

The essay on the Physical Geography of Belgium (1853) was the first book, M. Lancaster says, in which Houzeau "gave the measure of his force as a man of science and a writer, and in which one could perceive the whole extent and variety of his knowledge, appreciate his expository talent, and enjoy the charm of his sober, clear, and elegant style. He had been collecting materials for it for ten years, and in doing so made the best use of his pedestrian excursions. The book is possessed of an interest that does not pall for an instant in the reading, and is described by M. Lancaster as one of the most remarkable works that can be cited. An important paper in the same line was a study of the influence by which the peculiar features of the relief of Belgian topography had been produced. In 1854, through the influence of his friend and former colleague, Liagre, Houzeau was temporarily