EDUCATIONAL APPLIANCES. 1011 



Testing of the laws of the lever of first and second class. 

 Examination of the properties of the balances. 



Experimental proof of the proposition that every part of a decomposed force 

 produces a corresponding effect. 



4O02b. Apparatus for showing the Propagation of Wave- 

 motions. C. Chzechovicz, Russia. 



For lecturing purposes, and intended to show the propagation of wave- 

 motion by a system of bi-filar pendulums suspended on movable levers. 

 By changing the plane of suspension, one is enabled to reproduce waves with 

 plane vibrations as well as with elliptical ones. 



4002c. Model of a Plummer-block, for use in classes. 

 4002 d. Model of a Chain-holder, for use in classes. 



4002e. Group, with photographs of models, for use in classes. 



M. J. Prugger, Munich. 

 4002 f. Glenny's Diagrams of Building Construction 



(10). Chapman $ Hall. 



4O02F. Bristow's Table of British Strata. 



^ ; 4 Chapman 3? Hall. 



4002f. Unwiu's Machine Details (16). 



Chapman fy Hall. 



4002 f. Patterson's Zoological Diagrams (10). 



Chapman fy Hall. 



4002 f. Goodeve's Steam Diagrams (15). 



Chapman $ Hall. 



4O02f. Etheridge's Diagrams of Fossils (6). 



Chapman fy Hall. 

 4002f. Anderson's Diagrams (2). Chapman $ Hall. 



4003. Arithmometer, by Martinet, for imparting the know- 

 ledge of metrical arithmetic and practical geometry. 



Alphonse Martinot, Belgium. 



It is composed of one thousand small cubes of the size of one centimetre. 

 Thirty-two of these are isolated, nine hundred and thirty-two others are 

 united in several groups, forming forty-two pieces. There are ten pieces of 

 two cubes, ten pieces of five cubes, thirteen pieces of ten cubes, bound 

 together in the shape of reglets, or scale boards, one piece of twenty cubes, 

 one piece of fifty cubes, and, finally, seven pieces of one hundred cubes, 

 bound together like plane tables. 



The apparatus is completed by four racks, into which, not only the isolated 

 cubes, but the greater number of the groups of cubes may be bracketed so 

 as to form, when united, the cubic decimeter, i.e., the 1,000. It is easy to 

 understand what intuitive power this apparatus places at the disposal of the 

 professor, for teaching children, and for making them understand, in what 

 may be called a material way, the principles of numeration, construction, and 



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