12G Mr Miller's Description of a New Fyvometer. 



whitish matter, separated and examined apart, was found to 

 consist chiefly of lithate of ammonia : under the microscope, 

 it was seen to be composed of granules of about g oV o ii^ch 

 in diameter, and acted on by nitric acid and heat, it yielded 

 the purple compound characteristic of lithic acid. The dark, 

 almost black matter, composing the principal part of the 

 excrement, under the microscope appeared as a very mixed 

 debris, amongst which sand, in very fine grains, was ob- 

 servable, bat nothing else, well defined. No doubt, it was 

 faecal matter, and it would seem to indicate that the centi- 

 pede is a coarse feeder. 



Barbadoes, October 31, 1847. 



Description of a new Pyrometer. By Mr Alex. Miller, Livei'- 

 pool. With a Plate. Communicated by the Author. 



Thermometers being found inapplicable to the measure- 

 ment of the higher ranges of heat, Musschenbroek, about the 

 year 1730, was led to make use of the expansion of metal 

 rods instead of that of mercury. Since that period pyrome- 

 ters and metallic thermometers, with few exceptions, have 

 been made on the same principle, though varying in form ; 

 the expansion of the rods being assumed as proportional to 

 the temperature. 



The exceptions to Musschenbroek's method may be briefly 

 noticed. Wedgwood's pyrometer is founded on the property 

 that clay possesses of contracting by heat. Achard's resem- 

 bled the common thermometer, semi-transparent porcelain 

 being substituted for glass, and a fusible alloy for mercury. 

 Mr Prinsep, assay-master of the mint at Benares, proposed 

 the employment of alloys of various metals, in diff"erent pro- 

 portions, which melted at Viirious degrees. The expansion 

 of air by heat has also been employed in the measurement of 

 high temperatm-es. 



The principle of the pyrometer that forms the subject of 

 this communication, in the opinions of those* in whose judg- 



* Professors Faraday and Melson. 



