APPARATUS FOR TEACHING MINERALOGY. 867 



4115. Photographs of the lecture-room table, showing the 

 provisions made for enabling the audience to see more favourably 

 any experimental demonstration, by employing screens behind the 

 lecture- table. Professor H. Landolt, Aix-la-Chapelle. 



APPARATUS FOR TEACHING MINERALOGY. 



4116. " Student's Elementary Collection of Minerals." 



^ J. R. Gregory. 



4117. Elementary Collections (four) of Minerals, Fossils, 

 and Rocks, systematically arranged, in polished wood cabinets; 

 fitted for the use of the student and science-class teacher, and 

 illustrating the various mineralogical and geological handbooks. 



Thomas J. Downing. 



4118. Minerals (24) for Blowpipe Analysis. In case, 

 for the pocket. Set I. Thomas J. Downing. 



4119. Minerals (24) for Blowpipe Analysis. In case, 

 for the pocket. Set II. Thomas J. Downing. 



4127. Apparatus for demonstrating the physical properties 

 of Steam and the Steam-jet. 



Dr. L. Bleekrode, The Hague, Holland. 



This apparatus is designed for the lecture-table, and consists in a copper 

 boiler, which is heated by a common gas-burner with six or seven flames. 

 The quantity of water it contains is sufficient to p.erform all the experiments 

 during an hour, so that it needs no feeding, and the strength of the material 

 permits the production of steam at a pressure of four to five atmospheres. 



The following experiments may successively be taken or illustrated one 

 after another : 



I. The principle of the water-gauge in a boiler. 

 II. The action of the safety-valve. 



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



IV. The boiling of water at a pressure higher than the atmosphere. 

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



VT. 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.) 



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