66 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[February, 



Turning and Mechanical Manipulation, intended as a Work of General 

 Reference and Practical Instruction, on the Lathe and the various 

 Mechanical Pursuits followed by Amateurs. By Charles HOLT- 

 ZAPFFEL, A. Inst. C. E. 



Mr. Holtzapffel looking at the dearth of works on the arts pro- 

 fessed by the mechanical engineer, has felt himself called upon to 

 bring before the public the results of his experience on a subject of so 

 much interest and value. It is fortunate, perhaps, for the mechanical 

 engineer, that turning and many other of his pursuits have for a long 

 period formed a favourite occupation with many wealthy individuals, 

 as thereby an amount of patronage has been conferred on the tool 

 maker, such as could have been obtained by no other means, and 

 which has powerfully conduced to the improvement of the tools used 

 in this important department, while many experiments have been 

 made at private expense, which could scarcely have been executed 

 by persons engaged in business. With a class of wealthy amateurs 

 to whom to look for supporters, Mr. Holtzapffel could scarcely have 

 rendered a more acceptable service than the production of a work, 

 which, both to the practical man and the amateur, must be of high 

 utility. Mr. Holtzapffel, in the resources of his large establishment, 

 and availing himself of the experience of his predecessors in the 

 firm, possesses many advantages for the task he has undertaken, and 

 seems to devote himself to it con amore. The treatment of it he pro- 

 poses to enter into at some length, and we can scarcely blame him for 

 this, as the public will profit by the extent of labour devoted to the 

 subject. 



The volume now before us is one of five, and is devoted to the con- 

 sideration of the various materials used. The second will discuss 

 the principles of construction and application of cutting tools ; the 

 third will treat of hand turning ; the fourth of complex or ornamental 

 turning, and the fifth of the principles and' practice of amateur mecha- 

 nical engineering. 



The description of the materials is distributed into three classes ; 

 the vegetable, the animal, and the mineral kingdoms. The description 

 of the various kinds of woods, not only developes new facts as to 

 their technical peculiarities, but illustrates their botanical characte- 

 ristics, a portion of the work to which Professor Royle has contributed 

 his valuable assistance. The materials from the animal kingdom, 

 which are treated with no less ability, include shells and mother of 

 pearl, bones, horn, tortoiseshell, whalebone and ivory. The materials 

 from the mineral kingdom, embrace clay, amber, jet, cannel coal, the 

 ornamental and precious stonPs,the metals and their alloys. To state, 

 however, that the work is limited to a simple description of these 

 materials, would convey an inadequate idea of its value, as it abounds 

 with practical descriptions of many important or interesting processes. 

 Thus we have observations on seasoning, softening, bending, and 

 colouring wood ; the manufacture of iron ; forging, hardening and 

 tempering of iron and steel ; the melting and mixing of metals ; and 

 the properties of alloys; casting and founding; wire drawing and 

 soldering. To the description ot tempering alone twenty-five pages 

 are devoted, and the subject is treated with a minuteness and ability, 

 which leuve nothing to be desired. 



The Atmospheric Railway. Observations on the Report of Sir 

 F. Smith and Professor Barlow. By Thomas F. Bergin, M.R.I.A. 

 Dublin: Hodges and Smith, 1843. 



Considerable controversy has existed on this subject, and a long 

 correspondence has taken place between Mr. Bergin and Professor 

 Barlow ; with respect to it, we, however, are more inclined to look 

 forward to the result of the great trial now in progress at Dublin, than 

 to depend upon any mathematical formula, upon the bases of which 

 no party seems to be agreed. The experiment will soon be satisfac- 

 torily settled one way or other, and the merits or demerits of the 

 atmospheric system, will be shown in all their extent. Mr.Bergin 

 has devoted considerable ability to the discussion of the subject, and 

 the many who saw reason to distrust Professor Barlow's deductions, 

 cannot do better than consult this pamphlet. 



Jl Series of Diagrams, Illustrative of the Principles of Mechanical 

 Philosophy. Drawn on Stone, by Henry Chapman, and Printed in 

 Colours, by C. F. Cheffins. Loudon : Chapman and Hall. 



The fourth and fifth parts illustrate the pulley, inclined plane and 

 wedge. The plan, which is that of giving practical and useful appli- 

 cations of the simple powers is well carried out, and thus both theory 

 and practice are at once brought to bear on the instruction of the 

 student ; while it is not only a good work for the machinist, but a n 

 excellent drawing book. The work contains so manv illustration 



valuable machines, that we feel ourselves still more strongly called 

 upon to urge the necessity of some letter-press explanations accom- 

 panying the plates, treating on the theory of the powers and their 

 several applications. 



The Literary and Scientifc Pocket Rook. By J. W. Gutch. 

 London : Lumley. 



This contains much valuable matter of reference, and as such, we 

 have much pleasure in recommending it to our readers. 



ON THE STRENGTH OF BEAMS. 



Sir — The problem proposed for solution by your correspondent " Con- 

 crete," at page 27 of the last month's Journal, is certainly one of great in- 

 terest and importance ; as he states, I believe, it has not been investigated 

 in any of the standard works on the strength of materials. Like all ques- 

 tions connected with the strains of beams, it is one which, whether consi- 

 dered theoretically or practically, is of the most complicated nature and of 

 great difficulty; particularly if investigated with mathematical accuracy. 

 There are so many data to such questions, varying in each particular in- 

 stance — so many circumstances which modify the general result — such as the 

 deflection of the beam, and consequent variation of the length of leverage, 

 the position of the neutral line, &c, that since the time of gables to the 

 present day, they have always been considered as questions of the greatest 

 difficulty ; and yet there is no subject connected with theoretical mechanics 

 more interesting to the engineer; none more useful, especially in the present 

 age, when timber and iron are so extensively used in the most stupendous 

 structures, the economy and durability of which depend so much upon the 

 proper application of mechanical principles. I am sorry to say, however, 

 that even now, there are many engineers, particularly those belonging to the 

 old school, and such as have not the least knowledge of the elementary 

 principles of mechanics, who will not admit its utility ; who, because such 

 men as Telford, Brindley, George Stephenson, and many others, have risen 

 to eminence by the mere force of their talents, unfettered by, what they 

 term, college knowledge, think that they may also jog on on the "thumb of 

 rule " system. And yet, how frequently have I seen these pseudo-engineers, 

 these practical men, who will not look into a book, for fear it should destroy 

 the originality of their conceptions, fall into the greatest errors from the 

 want of such knowledge. I shall merely state one instance. A resident 

 engineer of one of our railways proposed a plan for strengthening a timber 

 bridge on the line, and in order to test the efficiency of his improvement, 

 made a model of the bridge on the scale, if I recollect rightly, of one inch 

 to the foot; he found that the model would support a certain weight, and 

 thence argued in a truly practical manner, that as the bridge was twelve 

 times the model, it would support twelve times the weight ! Thus satisfac- 

 torily establishing the utility of his proposed improvement. To return to 

 the question to be solved. If we omit the consideration of the deflection of 

 the beam, the result will be simple and sufficiently correct for practical pur- 

 poses, and the problem in question may easily be reduced to that of finding 

 the dimensions and form of a beam resting loosely on two supports, neces- 

 sary to sustain a given weight, (in this instance 42 tons,) placed at the centre 

 of the beam. 



Tour correspondent states that he found upon experiment, that a bar iron* 

 loaded, as he describes, broke near the two supports; this certainly is strange^ 

 and contrary to what we should expect theoretically and practically ; for 

 it is evident that the beam between the two supports is more curved at the 

 centre than near the supports, and consequently the strain, being measured 

 by the tension of the fibres, must be greatest in the centre, and gradually 

 diminish to the point of support. 1 have several times repeated his expe- 

 riment on a small scale, using, however, wood instead of iron, and have 

 always found that the wood broke in the centre between the supports ; of 

 course with the same proportion of external and internal parts mentioned 

 by your correspondent. 



It is also clear, from the principle of the lever, that the strain at the 

 centre of the beam, is the same as that produced by a weight of 42 tons 

 placed there, except that the action is reversed: the upper side of the beam 

 will now be compressed in place of being extended, and the under side ex- 

 tended instead of being compressed. If what I have advanced be correct, 

 as I believe, it will result that the best form to give to the beam is the para- 

 bolic ; that is, the depth of the beam should be greatest at the middle point 

 and diminish at the ordinates of a parabola towards the supports. As the 

 reasons for assuming this form to be the best, are given in all works on the 

 strength of materials, it would be useless to repeat them here. It is gene- 

 rally considered best to have the curved side of the beam upwards in such 

 a ease, but as in this example the action is reversed, it follows that it would 

 be advisable to have the curved side downwards. As your correspondent 

 only states the proportion of the distances of the weights from the points 

 of supports to that between them, it is impossible to give the exact dimen- 

 sions. I have not thought it necessary to give a diagram, as I believe, this 

 explanation may be easily understood from the description, and by referring 

 to that given by your correspondent. 



