Page:Popular Science Monthly Volume 13.djvu/527

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arate images presented to the brain, one blurred and indistinct, even for faces a yard distant, and the other clearly defined for objects at ordinary distances. "How is it," he asks, "that my brain or mind rejects the blurred image, and chooses the distinct one? . . . . If I get a particle of dust in the good eye, or close it, I immediately see the blurred image. . . . This blurred image always appears at a higher level than the other. Things appear as a rule," he adds, "much flatter to me than to people who enjoy binocular vision. I know this because I have a pair of spectacles so arranged as to equalize my sight. When I put them on, objects like trees put on a delightful fullness and roundness to which I am usually quite a stranger. I may add that two of my brothers have a similar defect of vision."


The Cactus as a Lava-Breaker.—A citation, in the bulletin of the Torrey Botanical Club, from Dr. Peters, the famous asteroid-hunter, gives an interesting fact in relation to the doctor's earlier days, when he ate prickly pears, or the fruit of the Indian-fig cactus, on the sides of Mount Etna. He describes the lava-beds as covered with impenetrable patches of Opuntia ficus Indica the Indian fig-cactus. These patches are the result of economic planting, with the intention of producing soil on the lava-beds. The Sicilian throws down a handful of soil, then drops upon this a bit of the cactus, which immediately roots. The effect of this cactus-growth is to facilitate the weathering of the rock, and thus make soil. The next step, after clearing off the cactus, is to plant fig-trees. In this way the lava-beds of Mount Etna are transformed into fruitful gardens.


A New Septic Organism.—Mr. Dallinger lately gave, before the London Royal Society, an interesting account of the life-history of a peculiar microscopic organism discovered by him in certain decomposing fluids. This organism never exceeds the 14000 of an inch in long diameter; in shape it is oval; at its anterior extremity it has a head-like protrusion bearing a delicate flagellum. From the sides of the shorter or front segment of the oval project two long flagella, and these, as a rule, trail behind, one on each side. It swims rapidly, but has also the capacity of anchoring both of its lateral flagella to the floor of the microscope-stage, or to a decomposing mass in the drop of liquid in which it is examined under the microscope. By steadily observing it in the free-swimming condition, it may be seen to undergo self-division, the division beginning in the front flagellum, and proceeding until, by longitudinal fissure, a new lateral flagellum is made for each half. There are now two perfect organisms. The author confined his attention for some time continuously to one of the segmental portions, and succeeded in tracing the process to its ultimate results. Having so observed a number of the self-dividing organisms, he found that in the majority of cases, when the process of fissure ceased, there was simultaneous exhaustion of vital action, and death; but in a certain proportion of cases, in which fissure was not so long continued, there was a change to the amœboid condition, the lateral flagella being absorbed, and the body becoming oval with anterior flagellum only. It now swims easily, but only in a straight line. It soon comes in contact with a colony of the organism in the perfectly flagellate condition, attaches itself to one of them, which soon unanchors, and both swim away. In course of time their movements become sluggish; the sarcode of their bodies is palpably blending, they become quite still, except for amoeboid movements, and then become one oval mass. After three or four hours this pours out minute specks, which appear to develop into the adult form and size. The temperature of 142° Fahr. is fatal to the perfect organism; the "speck," germ, or spore, can bear with impunity a temperature of 250° Fahr.



The schooner Eothen, carrying the expedition to search for the relics of Sir John Franklin's party, sailed from New York on Wednesday, June 19th, under the command of Captain Thomas F. Barry, whose discovery of spoons bearing Sir John's crest, in the hands of an Esquimaux tribe, was the occasion of fitting out this expedition. Lieutenant Schwatka, Third U.S. Cavalry, will command the search-party, and will have for guide and interpreter Joseph Eberbing, "Esquimaux Joe" of Polaris fame. The