32 GENERAL DISCUSSION OF CLAYS. 



furance only the end which is held near the body 

 whose temperature is to be measured, will receive the 

 full force of the heat. The two wires connect with a 

 galvanometer, the deflection of whose needle increases 

 with the temperature at the point of the free end of the 

 wire couple. As at present put on the market, the 

 thermo-electric pyrometer, costs about |180 and this, 

 together with the delicacy of th3 galvanometer, has 

 tended to restrict its use. There is no reason however 

 why one should not be made and put on the market for 

 a much lower price. It is not necessary that the re- 

 cording instrument should be in immediate vicinity 

 of the kiln, but it may be kept in another room where 

 it is safe from dust and rough handling, and wires can 

 extend f'-om there to tl c kiln. This pyrometer is con- 

 sidered to be accurate to within 10 degrees Fnhr. 



SEGER PYRAMIDS. 



These consists of different mixtures of kaolin and 

 fluxes, which are compounded so that there shall be 

 a constant difference between their fusing points. 

 Segar's series were numbered from one to twenty, and 

 the difference between any twoiconsecutive numbers 

 is 36 degrees Fahr. A later series introduced by Cra- 

 mer runs from .01 to .022 with a difference of 54 de- 

 grees E'ahr. between their fusing points, 

 and in addition the higher numbers in 

 the Segar series have been extended from 

 number twenty up to number thirty-six. As these 

 cones have been, recently recalibrated, the fusing 

 points of the various numbers together with their 

 composition is given herewith.* 



* Taken from a recently issued circular of Thon Industrie Saboratorium in 

 Berlin, where the cones are and were originally made. 



