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VI FOREWORD

electricity. The same answer must be given for rheology, at least to the politician. There is scarcely any article that one can name which in some period of its construction or use is not subject to flow, ć.g., casting, forging, heat-treating, cutting, filing, polish-ing, painting, lacąuering, etc. The processes can be improved by a better understanding of the fundamenta! principles of the science. At first one would suggest that a structure like a Steel bridge is put in place with the very idea that it shall not move, but a moment's consideration will show that not only did the molten steel flow, but a different type of flow took place during the rolling processes and a still different type during the heat tempering and ageingprocesses. And even in use it is by no means precise to say that deformations do not go on. So that one may be tempted to say that rheology is concemed as much in how to make materials that will not flow beyond a smali and negligible amount as it is in what people generally think of as flow, usually hydraulic flow. It is well to free the public from a misconception that would otherwise arise. The rheologist has little or no interest in hydraulic flow,

Rheology, as a science, can only deserve the name of science when it possesses a large storę of knowledge whicli has been proved capable of organisation and co-ordination by means of fundamenta! theories and which not only aet as a stimulus to further theoretical expaniion, but at once serve to benefit industries which utilisc the conceptions of the science, This, ol course, ineludes good clear-cut definitions, many oł whicli are laeking at present. It involves instru-mcuts of precisiou for measurcinent, a certain minimum nomenclature to avoid eitliur confusion 1 ^clr®Tim!pcution; but it aLso cntails the sub-

stitution of various simple measurements to take the place of those now madę, which though simple enough to make, are highly complex in theory and, therefore, comparatively useless in practice.

In a few words, the chemist has been successful in arranging his invisible atoms in definite pattems, quite after the methods conventionally used by the contractor, with his bricks and blue-prints. The physicist has harnessed the electrons for tuming the motors of the world and he is now attempting to harness the protons. The colloid chemist has shown that there are aggregations of matter above the molecule, yarious sorts of groupings, e.g., in sus-pensions, emulsions, etc., but he has failed to obtain the definiteness that there appears with the other categories. It is for the rheologist to show how the association between molecules affects the properties of materials. This opens up a very broad field, sińce the contractor works with bricks of one standard size, whereas the rheologist works with molecules of many different although related pattems. Orienta-tion, polymerisation, thixotropy, condensation, are evidences of forces in play between the molecules as definite and precise as those in classical physics and chemistry. There is already reason for believing that rheology can supply relations which are simple and exact. This volume, being the first one of its kind, should find a very useful place.

The products of nature's rheological combinations are olive oil, milk, albumen, blood, rubber latex, etc., many of which we regard as important, if not elementary; they are looked at askance by the chemist as being impure, for he deals only with mixtures of a morę or less uncertain number of isotopes, which he calls his “ elcments.” It is beyond doubt that the rheologist is usually required to deal