III. - THERMOMETRY. 259 



13Z5a. Air Thermometer after Riess. 



Warmbrunn, Quilitz, $ Co., Berlin. 



1004. Trough for comparing Thermometers, provided 

 with in- and out-flow tubes for water, and stirring apparatus. 



Dr. J. W. Gunning, Professor of Chemistry at the " Athe- 

 nceum illustre" Amsterdam. 



The thermometers are placed in a movable frame, in which they may be 

 transported from one trough into another containing water of another tem- 

 perature. Two sheets of glass, placed on either side of the frame, prevent the 

 inner portion of the water from cooling. 



1005. Dial Thermometer, designed by L. E. Briihne, Ley den. 

 Dr. D. de Loos, Director of the Secondary Town School, 



Ley den. 



This thermometer is intended to admit of a large number of students seeing, 

 from a distance, the change in the volume of the mercury as the temperature 

 varies. 



In the mercury is a small glass tube, balanced by another similar tube, both 

 being joined together by a thread, which is suspended over a small copper box, 

 at the extremity of which is a needle moving over a dial. 



1006. Mercurial Dial Thermometer, adapted for class 

 experiments on specific and latent heat. 



Prof. W. F. Barrett. 



The expansion of the mercury in the bulb of the thermometer lifts a small 

 iron piston which communicates its motion to the index hand. Small varia- 

 tions of temperature are thus readily seen by a large class, e.g., the expansion 

 of the glass of the bulb causing a momentary retreat of the index hand, is 

 seen to be the first effect produced by heat on the bulb. By making the scale 

 on glass the dial can be projected on a screen and determination of specific and 

 latent heat made before a large class ; electric contact can also be made by 

 the hands, and thus a self-registering thermometer constructed. The instru- 

 ment was made by Mr. Yeates, of Dublin. 

 \-A-\ t+ t - 



1011. Various Thermometers, of different kinds, in metal, 

 ivory, porcelain, glass, and wood. Elliott Brothers. 



' 



1012. Standard Thermometer. Elliott Brothers. 



1013. Insolation Thermometer, for determining the inten- 

 sity of the rays of the sun (maximum thermometer), with holder. 



' BerliH ~ 



1O14. Eight Normal Thermometers, executed by Greiner 

 and Geissler, Berlin. 



Imperial Admiralty Hydrographical Bureau at Berlin, 

 and Deutsche Seeivarte, Hamburg. 



These thermometers are employed in the stations of the Naval Observatory 

 and in the Imperial Navy. o 491!} 



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