278 Mr. Daniell on a Ncvo Register-Pyrometer. 



Exp. 13. The iron bar was placed in the register V., and 

 having been previously heated was plunged into the same pot 

 of metal. The silver at first set about the black-lead and ad- 

 hered to it in a large lump. At the expiration of ten minutes 

 this was just melted off, and the instrument was raised out of 

 the crucible in a perfectly clean state. When cool, the arc 

 measured was 7° 24' = expansion •064'5. 



Exp. 14. I made several attempts at the Royal Institution 

 to ascertain the melting point of cast iron ; but owing to the 

 large quantity of the metal necessary; to the difficulty of 

 keeping the temperature steady by constant feeding; and to 

 the failure of crucibles, — I did not succeed. I am under obli- 

 gation to Mr. Parker of Argyle-street, for the readiness with 

 which he afforded me every facility of performing the experi- 

 ment at his foundry. 



I selected a new register for the occasion, which was 

 marked I. Its rate of expansion was not determined till after 

 the experiment. A crucible was prepared capable of con- 

 taining about 35lbs. of the metal. It was filled with pieces of 

 the best gray iron, and placed in a powerful wind-furnace, 

 which admitted of the operator standing immediately above 

 the crucible with complete command over it. When the metal 

 was melted, the crucible was lifted from the furnace, and the 

 dross skimmed off its surface. It was then replaced ; a lump 

 of the same iron was thrown into it, and the register, pre- 

 viously heated red hot, was immersed in the fluid to about the 

 same depth as in the former experiments. It was kept in this 

 situation by means of a pair of tongs for ten minutes, and after- 

 wards gently lifted out and laid upon hot sand. A thin scale 

 of iron adhered to the black-lead, which when cold was easily 

 removed, and retained the form of the bar like a sharp cast, 

 and left the surface of the register perfectly clean and bright. 

 The arc measured after the experiment was 6° 16' = expan- 

 sion 'OS-l-e. Part of the lump of metal remained unmelted. 



Exp. 15. Another register, which had been prepared with 

 the iron bar, was immediately immersed in the fluid metal. 

 The fire, however, had been allowed to fall, and the iron al- 

 most instantly congealed ; and in attempting to lift the register 

 out, it was found to be set fast and broke. The experiment 

 was so far instructive, that it proved how nearly the exact 

 melting point had been attained in the preceding experiment. 

 The iron bar was removed uninjured. 



Exp. 16. The register I. with the platinum bar was boiled 

 in mercury for ten minutes : the arc afterwards measured was 

 1° 20' = expansion '0116. 



Exp. 17. About 30lbs. of zinc were carefully melted in a 



crucible 



