The large amounts of these losses indicate clearly the desirability (from the standpoint of the strength of the finished product) of using cement as soon after grinding as is practicable. It must not be forgotten, however, that cement which has had no aging is likely to be deficient in regard to soundness; so that its testing in respect to this requirement should be extremely thorough. The author for many years has insisted upon twenty-eight day tests on cement whenever that arrangement would not delay the progress of the work; but on the strength of Prof. Abrams' findings, he would now be willing to accept on seven-day tests any standard cement with which he is acquainted.

Again, the author has sometimes made arrangements for testing and storing large quantities of cement at the manufactory, so as to have it available when needed; but he may now be obliged to forego this practice.

Prof. Abrams' experiments were made on sacked cement; and he intends duplicating them upon cement shipped in bulk. Possibly the result of the new tests will show that keeping the cement in large masses will postpone somewhat the sudden drop in strength of concrete which occurs with cement two months old. It would be interesting to learn what the loss is on cement one month old; and it is to be hoped that Prof. Abrams will add to the value of his very useful experiments by settling this point.

Protection of Fresh Concrete

The protection of fresh concrete is an economic matter, as far as the contractor is concerned, because, according to all properly drawn specifications, he will have to make good at his own expense all damage done to the concrete through excessive cold or heat, or any other cause, before the final acceptance of the finished construction. It is also a matter of economy to the owner, because if the concrete is at all damaged, all the repairing that the contractor may do, short of entire removal and rebuilding, will fail to make the job as good and satisfactory as it would have been, had no such misfortune occurred.

General Remarks

From the point of view of both the engineer and his client, it is truly economic invariably to obtain concrete that is first-class in every particular—strong, solid, smooth, and hard—no matter how much it may cost; because failure of any kind in a reinforced-concrete structure is likely to be both serious and expensive. Many large bridges of that type, which were constructed under contracts secured through competitive bidding, show after a few years signs of disintegration. The ultimate result of such work is that the structure sooner or later will require either extensive repairs or entire rebuilding. The causes of such failures may be attributed to objectionable methods used by contractors in order to cheapen the cost of han-