APPARATUS FOB TEACHING MINERALOGY. 1043 



III. The relation between the tension of vapour and its temperature. 



IV. The boiling of water at a pressure higher than the atmosp"here. 

 V. The latent heat of steam and the warming system with steam. 



VI. The form of the steam-jet and its property of extinguishing fire. (Here 

 either the vertical or the horizontal valve may be used to lead the 

 steam on to some burning material.) 



VII. The producing of a vacuum by the steam-jet. (A metallic box may 

 easily be filled with the escaping steam, and as the box is afterwards 

 shut, it is depressed by the atmosphere.) 



VIII. The Giffard's injector. "(A glass model is fixed to the horizontal valve.) 



IX. The steam producing sound, illustrating the steam-signal and fog-signals . 



X. The steam sand blast. (This interesting experiment is performed in 



a very simple and yet satisfactory manner, by allowing the sand 



falling through a vertical funnel to mix with the horizontal escaping 



steam-jet, at the mouth of the valve.) 



XI. The electrical properties of the steam-jet. (Armstrong's hydro- 

 electric machine.) 

 XII. Heat producing work. (Principle of thermo-dynamics.) (Here a 



model steam-engine is connected with the horizontal steam valve.) 

 The chief advantages of this apparatus (already used in several institutions 

 in Holland and Germany) are 



1. It allows, with very little expenditure of time and heat, the illustration 

 of the fundamental principles of heat on the lecture table. 



2. It 'produces steam of high pressure, the properties of which may be 

 shown with very little danger. 



3. The relatively small expense (10/.) renders possible the introduction of 

 this apparatus into schools where physics and mechanics form an importan 

 part of the system of education. 



MISCELLANEOUS. 



4192a. Cosmographic Apparatus for teaching purposes. 



Letellier, France. 



4193. Stativ (stand), with a fixed and a movable pulley, besides 

 string and counter-weight. 



4194. Polyspast , to be appended to the same stand, with 

 four pulleys, string, and counter-weight. 



4195. Lever Apparatus, with attached needle (for the 

 balance) and stand. 



4196. Twenty-one Weights belonging to the foregoing objects. 



Royal Prussian Chief Mining Department, Breslau. 



4197. Oscillating Machine (centrifugal apparatus), with the 

 following auxiliary apparatus : 



a. Two-fold brass ring with iron axle. 



b. Glass globe with axle. 



c. Glass cylinder with inserted Sieboglinder (centrifuge). 



d. Double pendulum regulator with throttle-valve. 



e. Two balls, joined to each other by a chain. 

 /. Balancing ruler with sliding weights. 



Royal Prussian Chief Mining Department, Breslau. 



3U 2 



