To-day the young engineer frequently finds a good working knowledge of cement one of the essentials of success, and the gaining of this knowledge by experience alone is likely to be too slow and expensive, judged by twentieth century standards. In fact, the variety and extent of the uses to which cement is applied, and the knowledge concerning its properties, have of late increased so rapidly that even the older engineer, whose practice may have directed his special attention along other channels for a few years, finds it difficult to follow its progress.

One who wishes only a catechetical reply to any question that may arise concerning cement and its use will be somewhat disappointed in these pages; on the other hand, he who would devote special attention to the subject must, of course, go far beyond them. The author has attempted to take a middle course, avoiding on the one hand a dogmatic statement of facts, and on the other too detailed and extended series of tests, but giving, where practicable, sufficient tests to support the statements made, and endeavoring to show the connection between theory and practice, the laboratory and the field.

The original investigations forming the basis of the work were made in connection with the construction of the Poe Lock at St. Marys Falls Canal, Michigan, under the direction of the Corps of Engineers, U. S. Army. To the late General 0. M. Poe, the Engineer officer in charge of the district at that time, and to Mr. E. S. Wheeler, his chief assistant engineer, may be credited a very large share of the value of the results obtained, since the accomplishment of a series of experiments of so comprehensive a character was made possible only through the broad views held by them as to the value of thorough tests of cement.

The author wishes to express his appreciation of the courtesy of General G. L. Gillespie, Chief of Engineers, U. S. A., in granting permission to use the data collected, and of the kindness of Major W. H. Bixby in presenting a request for this permission.

When not otherwise stated, the tables in the work are condensed from the results of the above mentioned investigations. In supplementing this original matter, much use has been made of the experiments of others as published in society transactions, technical journals, etc., to all of whom credit has been given in the body of the work.

If this attempt to place in one volume a connected story of the properties and use of cement serves to make the road to this knowledge a little less devious than that followed by the writer, the latter will be rewarded.

L. C. S.

Sault Ste. Marie, Mich. January 3, 1905.