I84S.J 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



25r 



-thousands may prohably depend on the construction of these works with a 

 due knowledge of the mechanical sciences ; it becomes a matter of direct 

 public interest that those to whom the task is confided should possess a 

 tystemalic knowledge of their profession. That the importance of this 

 knowledge is becoming publicly recognized, we have a gratifying proof 

 in the condition of the College at Putney, and the results of the recent ex- 

 aminations there. 



We have to regret that the limits of our space will not permit, at present 

 « detailed account of the course of the examination, and an analysis of the 

 printed examination papers now before us. We can do little more than re- 

 cord the names of the students who obtained honorary distinctions, and 

 principal circumstances of the annual meeting, which took place on the 21st 

 June, for the distribution of these rewards. The following is the list of 

 prize-mea. 



MATHEMATICS.— 1st Class, Stephenson. 

 „ iilmrp. 

 2nd Class, W. Clark. 

 3rd Class, Coghlan. 

 CHEMISTRY.— I.alloralory Class, Newsoine. 

 Ward. 

 1st Class. Codrington. 

 2nd Class, Bennett. 

 GENERAL CONSTRUCTION AND ARCHITECTURE.— 1st Class, Sltpheusoii. 



2nd Class, W. Claik. 

 8rd Class, Crump. 

 UACHINERY.— Ist Class, Dratiing Prize, Male. 



2ad Class, ditto, Hawsen. 



Examitiation, Willett. 

 GEODESY. — Trigonomptrical Surveying, StepiieuBon. 



Ordinary Survey and I'lan Drawing. Coghlan. 



Dilto, 3rd Class. Christie. 



Military Class, F. Davidson. 



„ the Hon. P. Feilding. 



UANUFACTUBE OF IRON AND GENERAL PRACTICE OF MACHINERY.— 

 Pontifex. 

 Descriptive Geometry, sharp. 

 French, Baldry. 

 German. Hansen. 

 Landscape Drawing, F. Davidson. 



The chair was taken shortly after two o'clock by the Duke of Buccleucb, 

 who called upon the Reverend the Piincipal to read the report detailing the 

 examination. Of these reports we can say no more than they must have 

 been satisfactory to the most sanguine supporters of the Institution. The 

 certificates for prizes were given by the noble chairman to the students as 

 their names were successively mentioned in the Reports. 



The noble Chairman in the course of his address showed in very clear 

 terms the fallacy of the notion that mere professional " experience," un- 

 guided by preliminary systematic education, was sufficient for the purposes 

 of the engineer. He argued that modern engineeiing had made such ad- 

 vances and was now frequently applied to purposes so perfectly new and 

 Unprecedented, that cases must continually occur where the " rule of 

 thumb," as it was called, would be of no avail. He took occasion also to 

 compliment Mr. Cowie on the successful issue of his labous. 



The Bishop of London, in his usual felicitous manner, eulogised the moral 

 and gentlemanly deportment of the students. From living in the vicinity he 

 had taken great interest in this subject, and had uniformly found that his 

 neighbours concurred with him in giving the college this merit. Their tes- 

 timony was of the greatest value because founded on impartial personal ob- 

 servation. 



The Earl of Devon proposed and Sir Charles Lemon seconded a vote of 

 thanks to the Duke of Buccleuoh. Sir Charles Lemon observed that the 

 enlightened sentiments of the Duke had never been more conspicuous than 

 in his zealous support of the College, and his talents had never been belter 

 exhibited than in the clear views which his address contained of the results 

 of the system pursued in the education of the students. 



The following were among the noblemen and gentlemen present ; — Duke 

 of Buccleuch in the chair ; Bishop of London ; Earl of Devon ; Earl of Den- 

 bigh ; SirC. Lemon, M.P.; Sir J. Duckworth, A1.P. ; Hon. U. Howard; E. 

 Antrobus. Esq., M.P. ; the Right Hon. the Lord Mayor; Major Olephant ; 

 Gen. H. Thompson ; Col. Sykes ; Capt. Moorsom ; Col. Devereux ; Dr. .\r- 

 nott; J. C. Whiteman, Esq. Mr. Walker and Mr. Cubitt had both promised 

 to attend, unless prevented hy urgent business, and the Bishop of Oxford 

 sent a letter regretting that buisness prevented his presence at the College. 



A NEW THEORY ON THE STRENGTH AND STRESS OF 

 MATERIALS. 



Sir — Although I did not intend to answer queries, or discuss dilTerences 

 respecting the theory of ihe strength of materials, which I am advancing, 

 unlil I should have the whole developed, jet I Ihink it my duty to stop 

 and more fully explain one or two points lo whicl; you have alluded in 

 your laot number. My iheory is nut founded un Ihe idea, "that there 

 does not exist in deflected beams what is teimed a neutral line," yet I 

 deny the existence of a neutral line, or a neutitil surface as some wrilers 

 term it. Your definition of the neutral line dill'ers a little from that given 

 by Barlow, Tredgold, Moseley, &c.; be good enough lo look atTredgold's 

 flefiaitiou again, I gave it io my lirbt article. Moseley says, " One surface 



of a beam becomiuj;, when deflected, convex, and the other concave, it is 

 eviilent that the material forming that side of the beam which is bounded 

 by the oue surface is, in the act of flexure, extended, and the other com- 

 pressed. The surface which separates these two portions of the material 

 being that where its extension terminates and its compression begins, and 

 which sustains, iheiefore, neither extension nor compression, is called the* 

 neutral surfui-e.'' If jou look you will find that your deliuilion of the 

 neutral line dill'ers a little from this also. Vou say that " the originators 

 of the term neutral line staled that wheu a horizontal beam supporis a 

 transverse weight, the upper part of the beam exerts a thrust and the lower 

 part a tension ; and since these two portions of the beam exert opposite 

 kinds of action, there must be in the beam some intermediate part which' 

 marks ihe transition from one state to the other — where, therefore, there is 

 neilher thrust nor tension." Now this is the truth, but not the whole 

 truth ; consider two sections in a beam deflected by a weight, one in Ihe 

 centre and the other anywhere between that and one of the supports ; the- 

 compressions and extensions in these sections will dilTer in inleosily, and 

 if we suppose a libre v\ho.se breadth is very small, dx, if you please, I say 

 that the state of neutrality of this fibre, at one of these sectious, dillers ia 

 degree from that at the other, without reference to the action wiiich in- 

 creases or eudeavouis to increase the thickness of the beam at top and 

 decreases it at the lower part, which action has been neglected by every 

 writer on the subject. For argument sake, let the line which separatee 

 Ihe thrusts and tensions of every section be a mathematical line, then Ihe 

 only change that cau lake place in this line is in its length and deflection ; 

 then ask yourself the question, as the beam becomes loaded, is not this 

 neutral line, under one amount of pressure, longer and more deflected than 

 under any less aniouut. However, my great diflerence with other writers 

 is not about the neutral line or surface. Other writers might have estab- 

 lished their theory iodepeudent of the thickness of the beam, for they 

 state that no action lakes place in the direction of ihe breadth, that is, ia 

 the direction of your axis of Z. I show that there does exist an action ia 

 the direction of Z- I say that if a body becomes extended, or compressed, 

 its cross sectional area is diminished, or increased, or has a tendency to 

 dimmish or increase, although the cross sections present similar figures : I 

 am now speaking of the elongation of bars suspended vertically, and sus- 

 taining a given strain in the direction of their length. Other wrilers go so 

 far as to suppose that the cross sectioo remains the same till the body be 

 extended to ivvice its length ;— of this matter I will speak by-and-by. 

 AVhen you refer to fig. 3 of my last article, page 104, " he says," speaking 

 of me, 'that if a beam be deflected and a slice taken from tlie upiier pari 

 of it, this slice has the same form as the whole beam, and consequently 

 there is as much reason for assigning a neutral line to the slice as lo the 

 whole beam." You will find that I did not take a slice from the upper 

 part, and that I said, " the same process of reasoning which points out a 

 neutral axis in the wiiole, will point out a neutral axis io any portion ot 

 the body, no matter where it is situated." In this instance you will find 

 that I attacked the reasoning employed by others. Lower down it is 

 said, " For when he says ihat the Ibriu of the tUin upper slice is an argu- 

 ment for the existence of a neutral ia it, he makes the neutral depend 

 merely ou the form of the beam and not on the mechanical aciiun of its 

 pans." Vou will find that I said no such thing, nor made use of no such 

 argument; what I siid 1 will repeat; it follows immediately what I 

 quoted above, — " in fact, every fibre may be said to be compressed on one 

 side and extended at the other, while the whole or each is bent round a 

 common centre, entirely outside the body." When I select a porlioii I do 

 not take an upper slice, for I say, '• Now let us lake g-cdxt 1/9 : (fig. 3, 

 page 104), any poriiuu of tlie beam, it is evident that the tilameuts in the 

 upper part near dtq are expanded, and those near to xyz are compress- 

 ed ;" mark what I say, — " according to this reasoning there is a set of 

 fibres between iltq and xyz which are neilher compressed nor expanded ; 

 hence, etch poriiou of the beam is entitled to a neutral axis, which is rela- 

 ticetij correct, but eacli neutral axis is itsiilf bent round a centre." I hope 

 you do not mean to say •' tiiat the form of the beam is not inliuenced by 

 the mechanical action and connection of its parts," for I think that it will 

 not be denied that the mechanical action is influenced by the form, and also 

 that the form is influenced by the niechaoical action. I have got to the 

 place where jou say, '• We proceed now to ihe direct arguments establish- 

 ing the actual existence of the neutral boundary." Neutral wilh respect 

 to what? Neutral wilh respect to thrust and tension? Neutral wilh re- 

 spect to what degree of thrust and tension? You might as well try to 

 upset the truths of the mulliplicatioa table as 2(X) = 0, 2(V)-|- K— iW 

 = 0, 2 (Z) = ; aud you might as well try to undersland what ihe 

 author of ihe work on ihe ''Calculus," published by the Society for the 

 DitTusion of Useful Knowledge, means when he describes the third difl"er- 

 eutial cuefhcieiil, as to try to uudeisland what writers on tuis subject mean 

 by such terms as " the iulernal forces of he beamy' " the molecular action 

 of the forces in the cross section," &c. ; or, in other words, tlie equaiions 

 have nevf r been satisfied. If K = J W, it is evident that 2 (V) = 0, but 

 how is2(Y) made up? This would be of no consequence, only the 

 thrusts aud tensions of 2 (X) are uninfluenced by it. You, or rather the 

 writer of the arlicle in question, having despatched 2(Y), says, ■' similar 

 reasoning applies to the forces represented by 2(Z)"; uow this assertion is 

 not correct. 1 have before stated (page IG5, tig. 1 1) the nature of the actioa 

 of the particles in Ihe direction ol Hie axis of Z, so I need not dwell upon 

 the mailer here ; ami although 2 (X) = may be represented by ihe stati- 

 cal couple -{- M,— M, little is knowu with respect to iheir actual amount, 

 and as the distance between their points of appiicatiaa vary, your equation f 



