206 L. CASELLA'S CATALOGUE 



2399. DOUBLE CONE AND INCLINED PLANE, to show the descent of the centre of 



gravity, though the cone apparently moves upwards . 056 



2400. APPARATUS for demonstrating the parallelogram offerees, with weights and board 



complete, 18s. 6d. to . . . . . . 150 



2402. Attwood's Fall Machine, with large pendulum, in finely polished wood, carefully 



graduated ..... 10 10 



2403. APPARATUS to show that a body in rotating, if free, always selects the shortest 



axis . . . . . . . . 220 



2404. SMALL GROUND BRASS PLATES to illustrate the attraction of cohesion 12 6 



2405. COMETARIUM, for showing the elliptical orbit of a comet, laid off to explain the 



law of equal areas in equal times . . . . 2 15 



2406. GEOMETRICAL SOLIDS, in case, with book and illiiolrated text for stereometry 



and stereography . . . . . . 086 



2407. TRINOMIAL CUBE DISSECTED, for showing the relation between geometry and 



algebra ; large, 7s. 6d. ; small . . . . 5 



2408. THE GYROSCOPE, a modification of Bohnenberger's machine, by M. Foucault, 



arranged to illustrate the following principles : That inertia is a property of 

 matter in motion, as well as when at rest ; that axial and orbital motion are 

 closely related, and that the speed of one may affect or regulate the other ; 

 that the unstable state of equilibrium retained by various bodies is explained 

 by the fact of their rotation ; that bodies in motion endeavour to maintain 

 their original plane of rotation ; that the power of overcoming the force of 

 gravity possessed by shots when fired from. Armstrong's gun is due to the 

 gyratory motion given to them by the internal formation of the gun. It also 

 illustrates beautifully the precession of the equinox. Price of the simple form, 

 on stand . . . . >. ; . 110 



2409. DITTO, compound or most complete form in cabinet . 2100 



A very interesting illustrated paper on the gyroscope and experiments performed with it by 

 M. Foucault accompanies each instrument. 



Working models of steam engines, see pages 208 to 211. 



MODELS OF CRYSTALS, 



Of very accurate construction, designed with the utmost care. 



2410. Glass Models, to illustrate the six systems of crystallography. The set of six, 



uniform with the 2 or the 3-inch, cube, 3 3s. ; uniform with the 4-inch. 



cube . 550 



1. THE CUBE, containing the Tetrahedron, Octahedron, Intersecting Cube, and Ehombic 



Dodecahedron. 

 2. THE SQUARE PRISM, containing the Acute and Obtuse Octahedrons, and Long and Short 



Square Prisms. 



. THE RECTANGULAR PRISM, containing the Ehombic Octahedron and Prism. 



4, THE OBLIQUE PRISM, containing the Oblique Rhombic Octahedron and Prism. 



5, THE DOUBLY OBLIQUE PRISM, containing the Doubly Oblique Octahedron and Prism. 



G. THE HEXAGONAL PRISM, containing the Obtuse Rhonbohedron, and Scalenohedron of 



Carbonate of Lime. 



