The principles of graphics statics - Clarke

The study of Graphic Statics, as a subject Sui generis has made but little progress in England, though the great value of numerous Graphic methods has long been fully acknowledged. While in many of the great Engineering Schools of the Continent the subject is deemed worthy of a professional chair, in England it is left to be gleaned almost hap-hazard. A method more or less is thrown into a course of teaching, according to the predilection, or dislike of the teacher for Graphic modes of procedure.

And yet the subject is valuable, not merely as a means to an end, but as a part of mental training. A mind brought up only on mathematical symbols is but half trained: the Graphic is the complement of the Analytical process. And the power conferred by Graphic method is to a large extent at the disposal of those who have had but little mathematical training. The writer once had occasion to explain a, practical application of the triangle of forces to a class of working men, who seemed at once to grasp and appreciate it.

The present work is an attempt to steer a middle course between the too pronouncedly abstract character of many of the numerous foreign treatises, and the too narrowly practical treatment the subject has received in England. Though confessedly incomplete, it will, it is hoped, prove suggestive, and may perhaps lead some of its readers to a further prosecution of a really fascinating study-one, too, in which very much still remains to be done.

In order to make the work self-contained, an Appendix is added, giving tables of the weights and strength of materials. By the help of these tables it will be found possible to apply the various constructions to actual practice.

The scale to which the figures are drawn is necessarily contracted, but it has been endeavoured to make these figures clear and easy to follow. It is perhaps necessary to apologize for the employment of a few words not yet quite naturalized in the sense here given to them. Thus “pressure” has been adopted for compressive stress, which has usually been termed “compression.” Using “pressure” in this sense, “compression” is available for the alteration of length due to “pressure.” Tension and extension are universally so used, and analogy seems to demand pressure and compression. The words “vector” and “stress centre” are also adopted, while “kern” has been borrowed bodily from the German. The latter word has no English equivalent which possesses a sufficiently suggestive meaning, and the thing meant - the locus of the stress centre under certain conditions - has hitherto received no English name.