On a piece of work involving, say, two large concrete mixers capable of mixing 300 yards of material each per day, there will be used 900 yards of stone and sand per day, which, on a ten─day basis, will mean a very respectable stock pile. This 9,000 yards of material, costing perhaps one dollar per yard, means an investment of $9,000 in stock pile, on which interest must be paid at the rate of, say, 6 per cent, or $2.00 per working day, which means a trivial item compared with the advantages derived from having a constant supply of material. The total cost of this stock pile, in addition to interest, is the cost of one re─handling of material out of the stock pile, which at 5 cents per yard would be $450. This amount is very much less than the damage that would accrue from not having any stock pile at all. On most concrete jobs, there is usually provided a large storehouse for cement; and when the work has to go over from one working season to another, it is frequently the custom to leave the cement in storage. This is frequently a cause of loss of money, because the cement, being hygroscopic, absorbs moisture from the atmosphere, and is liable to spoil in consequence. This can be avoided by keeping the storehouse dry and warm through the winter, but this again is an expensive matter. =Old versus New Machinery.= In planning construction work, the question always comes up as to whether to use old or new machinery. No hard and fast rule can be prescribed. A case occurred upon an important contract where there were needed some new boiler tubes for the boiler that ran the main supply pump. The purchasing agent of the contracting company, who happened also to be the President and Chief Engineer of the company, bought some second─hand boiler tubes, which were forthwith put into this boiler. The saving on the boiler tubes was probably $8 or $10. The loss caused by a breakdown of the same boiler was nearly $50. In purchasing second─hand material, if the material can be thoroughly and rigidly inspected, it is perhaps wise to purchase it, and sometimes money can be saved; but as a general proposition, no second─hand material should be purchased for a contract, unless it is done with the determination of putting this material in first─class condition before it is used. The best inspection, as a general thing, will not disclose the exact condition of old material. By this it is not meant to intimate that new material should be purchased for every new contract.