230 SEC. 8. HEAT. 



1075a. 'sGravesande's Ball and Ring Pyrometer, for 



showing expansion. Harvey r , Reynolds, and Co. 



1076. A Musschenbroek's Pyrometer from the first half 

 of last century, with five different metal bars, and an autograph. 

 Property of His Highness Prince Pless, Schloss Fiirstenberg. 



Committee of Breslau. 



The apparatus has been constructed after the description and drawing 

 given on p. 12 and Table XXX. of Musschenbroek's "Tentamina Experiinen- 

 " torum Naturalium Captorum in Academia del Cimento, Lugduni, 1731 

 " Pars. II." The orthography of the French, on an annexed slip of paper, is 

 that of the beginning of the last century. The instrument, which is in capital 

 condition, may therefore be considered as one of the oldest of its kind. 



1078. Early Pyrometer (by Funiey). 



Museum of Physical Apparatus, King's College. 



1079. Daniell's Pyrometer, employed in researches by 

 Professor Daniell. 



Museum of Physical Apparatus, King's College. 



1077. Bailey's Patent Civil Engineer's Pyrometer, for 



ascertaining the temperature of flues, &c., with sheath and box- 

 wood handle to enable managers of works and others to carry 

 it about with them for use when necessary. W. H. Bailey ? Co. 



1080. Bailey's Patent Flue Pyrometer, for testing [the 

 temperature of boiler flues, hot-air chambers, stoves, galvanisers, 

 &c. W. H. Bailey $ Co. 



1080a. Hobson's Patent Hot Blast Pyrometer. 



Joseph Casartelli, Manchester. 



In this instrument the aim is to tone down the temperature of the blast by 

 an admixture of a constant proportion of cold atmospheric air, so that the 

 highest temperature likely to have to be recorded is brought within the range 

 of a good mercurial thermometer. The hot blast is introduced in the form of 

 a jet, which by suitable arrangement is made to induce a stream of atmospheric 

 air ; the mixed stream then passes on, and impinges on the bulb of the thermo- 

 meter. The scale has been laid down by experiment, and the instrument gives 

 the same reading as Siemens' copper ball pyrometer. It is found that pressure 

 does not affect the result ; and, as all the instruments are made exactly alike, 

 the same result is invariably obtained. By the use of this instrument much 

 time is saved, and the result is more reliable than with any other instrument 

 in use. 



lOSOb. Casartelli's Improved Pyrometer, for ascertaining 

 the temperature of flues, stoves, &c. 



Joseph Casartelli, Manchester. 



This instrument consists of two different metals of different ratios of expan- 

 sion, and any permanent set which may take place in the metals is compensated 

 by the fact that the set will take place in opposite directions. The scale is laid 

 down by experiment. It is so constructed that it is only necessary to expose 

 one half of the stem to the action of the heat. 



