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SPEYEK, JAMES 22 SPHEX financial and industrial organizations. He presented to the Teachers College of the Columbia University the Speyer School in 1902, and was trustee of Columbia and a director of several other educational and philanthropic institu- tions. SPEZZIA, a Greek island at the en- trance to the Gulf of Nauplia; area, 6V2 square miles; pop. 6,899, engaged chiefly in commercial pursuits. The town of Spezzia has a good harbor, SPHALERITE, or ZINC BLENDE, Native Zinc Sulphide. Also known as Blende and Black Jack, the iron which it usually contains giving it a black color. It is an important ore of zinc, con- taining approximately 67 per cent, of the metal. It is very widely distributed. SPHERE, in astronomy, a term for- merly applied to any one of the concen- tric and eccentric revolving transparent shells in which the heavenly bodies were supposed to be fixed, and by which they were carried so as to produce their ap- parent motions. The word now signifies the vault of heaven, which to the eye seems the concave side of a hollow sphere, and on which the imaginary cir- cles marking the positions of the equator, the ecliptic, etc., are supposed to be drawn. It is that portion of limit- less space which the eye is powerful enough to penetrate, and appears a hol- low sphere because the capacity of the eye for distant vision is equal in every direction. In geometry, a solid or volume bounded by a surface, every point of which is equally distant from a point within, called the center. Or it is a volume that may be generated by re- volving a semicircle about its diameter as an axis. The distance from any part of the surface to the center is called a radius of the sphere. Every section of a sphere made by a plane is a circle, and all sections made by planes equally dis- tant from the center are equal. A cir- cle of the sphere whose plane passes through the center is a great circle; all other circles ai'e small circles. All great circles are equal, and their radii are equal to the radii of the sphere. The surface of a sphere is equal to the product of the diameter by the circum- ference of a great cii'cle; or it is equiva- lent to the area of four great circles. Denoting the radius of the sphere by r, and its diameter by d, we have the fol- lowing formula for the surface: s = 4pr = pd-=:3.14159 . . d The volume of a sphere is equal to the product of its surface by one-third of its radius. It is also equivalent to two- thirds of the volume of its circumscrib- ing cylinder. The following formula gives the value of the volume of any sphere, whose radius is r and diameter is d: V := f pr'. Spheres are to one an- other as the cubes of their diameters. In logic, the extension of a general conception; the individuals and species comprised in any general conception. The doctrine of the sphere is the appli- cation of geometrical principles to geog- raphy and astronomy. An oblique sphere, or spherical projection, is the projection made on the plane of the horizon of any place not on the equator or at the poles. SPHERICAL TRIGONOMETRY. See Trigonometry. SPHEROID, in geometry, a solid, re- sembling a sphere in form, and generated by the revolution of an ellipse about one of its axes. If an ellipse be revolved about its transverse axis, the spheroid generated is called a prolate spheroid; if it be revolved about its conjugate axis, the spheroid generated is called an ob- late spheroid. The earth is an oblate spheroid — that is, flattened at the poles so that its polar is less than its equa- torial diameter. SPHEX, a genus of hymenopterous in- sects of the family Sphegidse, closely allied to the true wasps. The sphex wasps are solitary in habit, and there are no workers as in the social forms. The female hollows out, at the end of a long passage, three or four chambers, in each of which she deposits an egg and a store of food for the larva she will never see. The food consists of gi-asshoppers or other insects, and Fabre gives a minute account of the way in which the sphex attacks her victim, and, after a long and violent struggle, throws it on its back and stings it in the neck and between the thorax and abdomen, each time piercing a ganglion. The in- sect, completely paralyzed, but alive, and therefore not liable to putrefaction, is then dragged to the mouth of the nest, where it is relinquished for a short time while the wasp enters alone to see that all is right. So automatic is this habit of reconnoitering that if the grasshop- per be removed a little distance the wasp drags it back to the same spot and again enters alone. This was tested by the ob- server 40 times in succession, and each time the wasp paid her preliminary visit of inspection. Four paralyzed insects are placed in each chamber, which is sealed up as it is finished. When all are full the mouth of the passage is also closed, and the nest is abandoned.