Excerpt from Electrical Resistance and Critical Ranges of Pure Iron Whether or t either or both of these critical ranges, A2 and A3, are to be considered an allotropic point will depend on the definition of allotropy, about which there does t yet appear to be agreement. The reversible thermal and electrical behavior at A2 appears to be somewhat similar to that of a pure substance at its melting point, while at A3 there is a progressive change with temperature of the electrical and thermal properties which are t reversible, the reaction taking place at a higher temperature on heating than on cooling. The A3 change is certainly associated with recrystallization, while crystallographic change has as yet been found at A2, which is also the temperature associated with the abrupt, reversible change of iron from the ferro-magnetic to the para-magnetic states. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art techlogy to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.