The demand for practical instruction in all branches of a subject in our Technical Schools is increasing, and the introduction of experimental work is so moulding the character of the teaching, that the teacher must keep himself conversant with the new developments that are constantly arising in consequence of the progress of scientific knowledge. In accordance with these views the author has made a special study of the intimate structure of metals during the last few years, and found great pleasure in following the researches of those who may be rightly termed the pioneers in metallography, such as Sorby, Martens, Osmond, Stead, roberts-austen, Arnold, Andrews, and several others, whose patient and laborious efforts have brought to light such a precious fund of knowledge that many of the hitherto unsolved problems have now received a satisfactory explanation. As far as the author is aware of, no book on the subject has before been published in. The English lan guage; and as metallography is yet in its infancy, it is not sufficiently developed to permit of its being placed on a strictly logical scientific basis. This is therefore only an attempt to lay the principles of the subject before students and workers who are interested in the' properties and applications of metals, and to offer a series of original illustrations which it is hoped will assist in making the meaning clearer.