278 SEC. 8. HEAT. 



" Salinenwesen, im Preussischen Staate. Herausg. im Minist. fiir 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. 



11 05 a. Apparatus for quickly communicating a Given 

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

 W. Gloukhoff, Warden of Russian Standard Measures. 

 It is used in the determination of the density of the liquids ; for the 

 verification of alcoholometers, 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 disc, covering the 

 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 ther- 

 mometer to determine the temperature of the liquid. 



llO5b. Apparatus for keeping a Constant Temperature 



in an air or water bath. 



The Secondary Government School, Assen (Netherlands), 



This gas regulator, constructed after the design of Dr. A. Van Hasselt, 

 teacher at the school for middle-class education at Assen (Netherlands), was 

 made principally by J. Van Eossum, servant in the laboratory. 



The air thermometer, connected with the regulator and with a large Bunsen 

 cell, is partially filled with mercury, so that only the upper bulb and a 

 great part of the tube contain air. 



When the desired temperature has been reached, the wire of platinum is 

 screwed down, so as to reach the mercury, at which moment a current from 

 the cell passes. This current passes through the wire, which is coiled round 

 the iron tube in the apparatus, through which the gas is flowing, and which is 

 used as an electro-magnet. 



The little iron valve on the side of the tube, covered with a thin plate of 

 caoutchouc, which now shuts the tube, has a small aperture, which lets pass 

 gas enough to prevent the lamp from being extinguished. 



