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THE POPULAR SCIENCE MONTHLY.

est-continued convulsions, M. Delaunay suggests, take place when two large planets pass by the cosmic groups at the same time. Of this character were the earthquakes of 1755, 1783, 1829, and 1841. Accepting these principles as the laws regulating the occurrence of earthquakes, and admitting that certain of the cosmic groups may have a slow oscillatory motion around a mean position, it is not difficult to predict when earthquakes may be looked for. M. Delaunay ventures to predict the dates at which the earthquakes to occur between this time and 1920 will, according to his theory, be due. The most important earthquake periods will probably occur in the years and groups of years 1886, 1890-'91, 1898, 1900'01, 1912-'13, 1914, 1919-'20, The next seismic tempest may be expected to follow the passage of Jupiter through the zone of the August meteors in 1883.

 

Do Stenches cause Disease?—The people of Paris were frequently annoyed during the last summer by the presence of mephitic odors in the atmosphere. A commission, appointed to discover the origin of the smells, traced them to certain establishments in the neighborhood where refuse matter is manufactured into fertilizers. M. Bouchardat, of the medical faculty of Paris, has examined the question of the effect of these emanations upon health, and has concluded that they are innocent. He does not believe that they convey with them the germs of disease, and finds that the gases of which they are composed do not load the air enough to produce a perceptible poisoning. Moreover, no injury to health has been traced to them. Assuming that contagious diseases should manifest themselves within eight or ten days after the germs have been planted, the weekly health bulletins of the year have been examined to learn if any increase of mortality followed the prevalence of the unpleasant odors. No such increase has been detected, but the mortality seems rather to have fallen off.

 

Mr. Thomson's Journey in Eastern Africa.—Mr. Keith Johnston was dispatched by the London Geographical Society, in 18*78, with an exploring expedition to East Africa, charged with examining the country in the neighborhood of Lakes Tanganyika and Nyassa. Mr. Johnston died at Behobeho, just at the borders of the objective region of the expedition, on the 23d of June, 1879, and the whole responsibility of the undertaking fell upon Mr. Joseph Thomson, his geologist and general assistant, a young man twenty-two years of age, to whom this was almost the first serious experience in life. Mr. Thomson gave a most interesting account of the expedition, which was attended by unexampled success, at a meeting of the Society on the 8th of November last. His story is enlivened with accounts of different tribes of the most diversified characters and degrees of civilization, living by the side of one another. Leaving Behobeho on the 2d of July, the expedition went toward the west, into the country of the Wakhutu, passing through the valley of the Mgeta, where perennial showers precipitated from the high mountain-range on the right, which forms the ridge of the great central plateau of the continent, stimulate a tropical vegetation to grow and rot in marshy tracts. Under the influence of such an enervating and malarious climate, the Wakhutu are one of the most miserable and apathetic races to be found in Africa, and presented a disgusting sight to the traveler as they gathered around him in crowds, “sitting with their miserable, withered bodies doubled up, and idiotic, lack-luster gaze.” Their neighbors, the Mahenge, a hitherto unheard-of tribe, living between the Ruaha and Uranga Rivers, were brought several years ago in contact with a migration of Zooloos, and have adopted the arms, dress, and manners of those people, although in other respects having no affinity with them. To the Wakhutu the Mahenge are a warlike and dreaded tribe; to the English traveler, “they were a set, of most arrant cowards, a mean, sneaking, lying race, unworthy of the name of men.” Ten days were occupied in crossing the mountain ranges that bound the central plateau—a charming journey, with diversified scenery and luxuriant vegetation—after which the party entered upon a bleak, moorland country four or five thousand feet high, unrelieved by hill or dale or forest-tree. The scanty population of this barren district of Uhehe are settled in villages at very wide