OTAGO INSTITUTE

Otago Daily Times, Issue 16519, 20 October 1915, Page 2

OTAGO INSTITUTE

TECHNOLOGICAL BRANCH. The last of the meetings of the Technological branch of the Otago Institute for the current year was; held-in the physics room, Otago University, last night, when the annual meeting was held.. and a lecture; was delivered by Professor J. Park on "Strength of Materials." Mr J. Blair; Mason occupied the chair. ANNUAL MEETING. The report stated that the year just closed was the fifth of the existence of the branch. Despite the distraction of the war and the inevitable absence,of many members at the front and elsewhere, good and useful meetings had been held, with profit and satisfaction to . those who had participated in them. An innovation adopted by the committee had been the restriction of the meetings to the winter .months. It had not been thought advisable to attempt to continue the annual dinner for; the present. ' The adoption of the report and balance she«t. which showed the branch to be _in a flourishing condition, the balance. being over £18,..was moved by the Chairman and carriea. -.-■<.: ■ :.■;'■

The Chairman mentioned the matter of the room in,which the branch met. It was felt by some, and by the committee, that, the University was top far from the centre of the city, arid attendances_ might; be bettered were the place of meeting more aoces-' 6ible. A-suggestion had been made that a .inio'ru convenient room might be available in the centre of the city. The matter: was discussed by those present, to 'obtain 1 .: the. feeling of the meeting; and it was resolved, that the incoming committee be niended t° try and secure a morer central position. A vote of thanks -was passed vp the University Council for its kindness to "the branch in proViding.tbe use of a room so suitable to the requirements of Ahe branch as was that at present occupied. The' sum of £10 was voted to the funds of the Astronomical branch. , The following office-bearers were elected': President, Mr J. Blair Mason; vice-chair-men—Professor J. Park, Professor D. B. Waters, v and Mr B. B. Hooper; committeeMessrs G. W. DaviesJ, W. D. R; MlDurdie,

George Simpson, R,:N. Vanes, and.Mandenp; secretary, Mr ,H.'Brasch. ' : ''.". '". '..' . ..'■/i'-IKOTtTHE. Professor Park first • dealt with the theoretical conditions underlying the strength and design of. structures, arid later, with) the application of first principles,, on which, he said, all engineering practice depended. The strength of material, lay In its' ability to resist . deformation under ■ the influence of an external force. In the case of bridges there were two forces to,-, be considered: '■ dead, weight,-including that of the bridge, itself: and .any load applied suddenly and causing" vibration —a live load. A live load, would be such as a train in.motion, and such v "a,

load impdsed'at. least double the'stress that: would be set:up by a dead load of 'theVearoi* magnitude. The lecturer defined the terms; stress and strain; the former signifying' the force or forces acting ion a body,, and strain the change of shape resulting from stress. ■ When the stress was,beyond the limit of elasticity of'.the material the was strain or permanent deformation. The resistance a material ,-yiras able to oppose to an external force, depended on the manner in which the load .was > applied.

He r entered into v an . interesting, : his-, tory/of the growth of knowledge re-; gard' to formulae for 'beams and girders, and by the use of models, diagrams, etc.;. showed'i how, the reactions and .bending-movements in beams were The'first bridges' built by man were, he said, profoaMy a close imitation of Nature.' Most probably the .first was a log that had got thrpwn oyer a stream, and the first actually made by man would be similar. The. Gothic" arch, the strongest of all arches, was a pure, imitation of those rock bridge's to be found in mountainous country«and on the seashore. In the mountains such natural, bridges m course of time 'scaled away under the in- . fiuence of weather till they assumed the .perfect Gothic form, when scaling .ceased, leaving the permanent result. ; Driftwood and large tree trunks heaped over wide streams in flood-time would soon \show the way. to make permanent structures over rivers. Strange to say, there was no mention of any bridge in the Bible, closely identified though the Jews were twith Egypt and the Roman world; The, Romans were £reat bridge builders. The first bridge mentioned in any historical record occurred {in- the; .quaint Chaldean narrative of the Eall.'This narrative approximated closely to the Bibles version, but, as he'had said, the Bible-did not mention bridges. .:.' After 'leaving the Garden of Eden, Adam and Eve were penned up by thunder, and; rain, on a tongud of land at the junction of [the Euphrates and Tigris, and Adam "gathered a huge 'trunk;* threw it across .the stream, and passed over into the land_ of Ur." The rest of the lecture was of a highly technical character,;;dealing with the method of arriving; at,,the actual stress imposed upon' the various .beams and struts 'of bridges, and,: like theoretical problems. " '