VIII. MISCELLANEOUS. 237 



magnet, an electric alarm and indicator are set in motion, thus giving prompt 

 notice of the fire, and indicating its position. 



1101. Prism of Rock Salt, 50x60 mm. 



W. Steegr, Hamburg vor der Hohe. 



1102. Lens of Bock Salt, 75 mm. thick, and 300 mm. in 



radius. W. Steeg, Hamburg vor der Hohe. 



1103. Plate of Bock Salt, 60x60 mm. 



W. Steeg, Hamburg vor der Hohe. 



1104. Diagram of the Thermodynamic Relations of 



Aqueous Vapour for pressure up to 30 atmospheres. 



Oberbergrath E. Althaus, Breslau. 



These diagrams have appeared on a smaller scale, and joined to a memoir 

 entitled : The Boiler Systems for High Pressure, and their Application to 

 Mining Engines, Part III., in the " Zeitschr. fur das Berg-, Hiitten-, und 

 " Salinenwesen, im Preussischen Staate. Heraung. im Minist. fur Handel, 

 " Gewerbe, und offentliche Arbeiten. XXIII. Bd., 5 Lief." 



HO4a. Two Photographs, representing the Thermo -venti- 

 lator when open and closed. M. Wellesen, Christiania. 



This instrument, which is useful as a means of promoting health, consists 

 of five parts, comprising a regulating balance for heat, and a valve for fresh 

 air, which is self-closing, and can keep out the cold. The smaller part of 

 the iron and brass tube (to which a foot or stand is fixed for exhibiting pur- 

 poses) gives a clear idea of the system by which the thermo-ventilator is 

 applied to the internal orifice of the atmospheric tube. 



1105. Apparatus of sheet metal, constructed by the exhibitor, 

 for demonstrating the Causes of Disturbances in the Draught 



in Chimneys, as well as the influence of wind and weather. 

 It is at the same time a means of studying the general motion of 

 air produced by heat (ventilation). Compare the adjoined de- 

 scription. Prof' Dr. Meidinger, Carlsruhe. 



1105 a. Apparatus for quickly communicating a Determined 



Temperature to a Liquid, and to maintain it at this temperature. 



W. Glouhhojf, Warden of Russian Standard Measures. 



It is used by a hydrostatical determination of density of the liquids ; by 

 verification of alcohometers, hydrometers, &c. ; at normal, or any other tem- 

 perature. The principal part of this apparatus is a cylindrical metallic 

 stirrer, immersed in the liquid to be experimented upon, contained in a very 

 solid glass cylinder. The warm or cold water, poured in small quantities, in 

 the interior hollow space of the stirrer, by means of a glass funnel introduced 

 in one of the two metallic tubes communicating with the hollow space, and a 

 few movements up and down of a stirrer, will very quickly warm or cool the 

 liquid, and thus bring it to a determined temperature. The syphon, introduced 

 in another tube, serves to empty the stirrer. In the glass disk covering glass 

 cylinder are two apertures : the large one, for weighing solid bodies in liquids, 

 immersing in it the hydrometers, &c. ; and the small one for a thermometer 

 to determine the temperature of the liquid. 



