PHYSICAL TESTS FOR THE BLAST-FURNACE, ETC. 505
study of the subject to agree with him in advocating the principle of the round chill.
The tapering rule D, Figs. 115 and 116, is graduated on one side, as shown, to measure the contraction in the sixty-fourths of an inch. The rule is cut off on the small end at a point where it is one-sixteenth of an inch in thickness. From this the taper runs up two inches, at which point it measures three-sixteenths of an inch. The distance between the one-sixteenth and three-sixteenths points is then equally divided by six lines, as shown, so as to read to the one-sixty-fourth part of an inch, according as the space of contraction will permit the rule to be inserted between the chill-mould and the pig specimen, as shown. The lines being one-quarter of an inch apart, the scale can be easily read; but the rule could, of course, be graduated finer if desired.
The study of the element of contraction, as it can be defined from any pig specimens, Figs. 114, 115 and 116, will prove very valuable, and, in time, may enable a tester to know at a glance, without further research, the true " grade " of an iron. It can aid the furnace-man to detect deception, which is now known to exist in the fracture of " direct metal," and also to learn the true effects of re-melting iron, and what metalloids cause the greatest contraction in the iron.
At E, in Figs. 114 and 116, will be seen a depression of about one-quarter of an inch below the top surface of the chill-mould. This is to provide means for a *' flow-off,'' to insure the chill specimens being always of the same thickness and prevent any iron running over the edges of the mould to retard free contraction in any manner. The chill-mould, of course, is set level.cause any one making ad which is a forma warm ladle to receive the liquid iron. The lining used for the cupola is simply a coating ofnovice desires to use the smallest cupola practical for melting small samples. "............ " " i in square hnrH........................