TKAXSACTIOXS OF SECTION J, 433 



endeavoured to set forth a few points that have occurred to 

 me as hkely to excite thought in the minds of those who are 

 engaged ni building up our AustraHan cities. They may not 

 be reahsable at once, or in the exact form indicated, but of this 

 I am certam : that, if carefully weighed and considered, and in 

 due tnne acted upon, they cannot fail to effect a great improve- 

 ment, and help to produce cities in the future which, if not as 

 wildly picturesque as the Nuremberg of the past, will be more 

 useful, healthy, beautiful, and pleasant to live in than any this 

 quarter of the word knows at present. Some may say this is 

 only a dream ; but, if we compare the present with the past, we 

 may safely forecast the future. I cannot better conclude than 

 by quoting the words of Euskin, that " it is onlv possible to 

 answer for the final truth of principles, not for the direct suc- 

 cess of plans, and that in the best of these last what can be 

 immediately accomplished is always questionable, and what 

 can be finally accomplished inconceivable." 



1. Description of the Apparatus used in testing Materials, 

 ivith especial reference to Cast-iron, Wrought-iron, and 

 Steel. Tests to secure a Suitable Material. Safe Work- 

 ing-stresses, Fatig^ie, a^id Factors of Safety. 



By W. H. Warren, Whitworth Scholar; M.Inst. C.E. ; 

 M.Am.Soc.C.E. ; Challis Professor of Civil and Mechanical 

 Engineering in the University of Sydney. 



Plates VIII.-XIV. 

 The strength of a structure, such as a girder, a roof, or a 

 bridge, depends not only upon the form and dimensions of the 

 structure, but also upon the materials used in its manufacture. 

 The load or loads which a structure is designed to carry pro- 

 duce stresses in the various members, which may be tensile, 

 compressive, shearing, and occasionally torsional ; the stresses 

 develope resistances in the material, which are generally accom- 

 panied by slight alterations in form, such as an elongation or 

 a shortening of the member in question. The elongation or 

 compression, as the case may be, is termed the "strain," 

 which must not be confounded with the " stress" producing it. 

 The stresses which are produced in the various parts of a 

 structure depend entirel}- upon the form and dimensions of the 

 structure, and are independent of the materials used in its 

 manufacture ; but, in arranging the areas of the various parts 

 to resist the stresses produced in them, it is necessary to know 

 28 



