THE Method of specifying the proportions of Concrete material by so many loose volumes of gravel to a definite number of volumes of cement has much to commend it, for it is easy of application. To those using concrete, however, it has been apparent for a long time that to get the best results, those proportions must be determined by having regard to the nature of the aggregate. Many examples can be recalled in which a "lean" concrete has developed much greater strength than a much "fatter" one. A recent method of investigating the matter, especially by American Engineers, is to determine how much mortar, composed of three sand to one cement, will fill the voids in the aggregate of broken stone or gravel and to specify the quantities accordingly. These methods are more or less empirical and this investigation has been undertaken to ascertain, if possible, some definite standard of aggregate material; a more or less ideal substance, towards which one might approximate. Harry Jackson
Sir,-Referring to Mr. Andrews’ article in the Jsnuary issue of The Structural Engineer, the report which he quotes from was only intended to be a summary of the actual results obtained.
Between the Brunels and the Rennies there is a marked resemblance in that in both cases a distinguished father begat a distinguished son who was able to continue the work successfully initiated. A. Trystan Edwards
HAVING treated in broad general outline the subject of housing in the Netherlands, and having set out the difficulties that have been encountered in the course of the efforts made by the Dutch people to grapple with the various phases of this complex problem, and explained the measures invoked by the authorities in their endeavours to correct, the troubles produced partly by neglect in the matter of housing extending over a generation or two, and partly as the direct result of the great war, I venture to believe that it will be of general interest briefly to examine the methods of building adopted by the Dutch authorities, and the character, type and standard of the housing accommodation provided during the period particularly under review at the moment. Sir Charles T. Ruthen
There are two subjects which may be said to have gripped the imagination of engineering scientists for the past 70 years; they are the strength of columns and the fatigue of metals. Both have this in common that the further they are investigated the more we realise that, they are more complex than we previously realised, and that many of our previous ideas upon them have to be scrapped or revised. Hon. Editor
Most books on building construction still begin with the wall, while books on architectural design begin with the column. Guadet, whose "Eléments et Théorie" is much more practical than aesthetic, also starts off with the wall as the primal element from which all the complications of structure may be evolved. The teachers of design are no doubt by a good deal more modern than the teachers of construction, for the wall has ceased to occupy that position of eminence which it used to enjoy. Once the beginning and the end of structure, it has become as a garment spread over a structure to keep out the rain and the cold. For this purpose, at any rate, we shall always want it. The very humble position to which the wall has to-day been relegated is one from which it is not likely ever to be ejected. We must have walls to shelter us, though we no longer require that they shall sustain our buildings, a task which the column is to-day expected to fulfil. The time is bound to come, therefore, when our manuals of construction will begin with the column, and deal with that minor and quite non-structural adjunct, the wall, somewhere towards the middle of the book, if not at the end. The time will come, but before it comes the victory of science over tradition will have to be very nearly complete. To-day the two still manage to exist side by side without any manifestation of hostility, and our scientific text-books, which are daily adding many fresh adherents to the columnar persuasion, have by no means succeeded in extirpating the traditional mural school. Theatres and officeblocks may be built according to science, but our houses are still (though no one knows how long they will continue to be) built by the age-hallowed and leisurely process of laying brick upon brick which seemed to Mr. Wells of such antediluvian extravagance. Christian Barman