To the municipality, faced with residue accumulating from the refuse destructor, gas, and electric lighting installations, such a machine is virtually indispensable. It offers a complete economic solution to a perplexing problem. A certain amount of official building is always necessary, and concrete blocks with clinker forming the aggregate constitutes an ideal and inexpensive material. One great objection often raised against the utilization of cinder and other similar residue for this purpose is the dingy tone of the resultant block. But this need not constitute a handicap. If used for the external walls of cottages the concrete can be finished off in rough-cast, or may even be plastered and painted. In many instances excellent reproductions of half-timbered styles have been carried out in this material, and are far more substantial than those wrought in the conventional brick. But the chemist must be harnessed to the development, that is if the most satisfactory results are to be obtained. It is the tendency to ignore the chemist which has been responsible for much concrete failure for homes in the past. It is imperative that clinker refuse be analysed. If it be associated with fused glass it is useless for the purpose, for the simple reason that the smooth surface of the glass fails to afford the requisite gripping surface to the cement. Unless care be displayed in this connection disintegration of the block will set in, in which event the concrete will be condemned as a failure when, as a matter of fact, it is the ignorance of the individual and the presence of the glass which are responsible for collapse. Similarly it is essential that the aggregate should be free from organic material. This may be intensely dry when the mixing of the concrete is taken in hand. But the organic material will absorb the moisture after the manner of a sponge, continuing to do so until completely saturated. As a result of this action the material necessarily expands, and so will bring about the breakdown of the concrete. Therefore, if full advantage be taken of the chemist specializing in constructional material in the scientific preparation of concrete, as is done in Germany and the United States, failures will be few and far between.