1841.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



83 



The following examples will suffice to show the application of tlie for- 

 mulae : — 



Example 1. A cast iron beam of which the transverse section is a rectangle 

 (fig. 1). is supported horizontally on two props placed at the distance of 30 

 feet apart ; what load will the beam sustain at its middle point including the 

 effect produced by its own weight, its depth in the direction of gravity being 

 22 inches, horizontal breadth 3 inches, and specific gravity 7-372, that of 

 water being unity ? 



Tlie formula by which this example is resolved, is number 3 of the com- 

 partment for the strength of rectangular beams, and by substituting the nu- 

 merical values of b, d and /, we get 



■■(,bd- 7-6x3x22 



/ 



36 



= 306-533 cwts. 



If the beam were of Memel Fir of which the specific cohesion is 1-154, 

 that of the given material being 4-334 ; the strength would be found as fol- 

 lows : — 



4-334 : 306-533 : : 1-154 ; 81-62 cwt. nearly; and in this way the 

 strength may be calculated for any other material of which the specific cohe- 

 sion is known. 



Example 2. Let the length and depth remain as before, what must be the 

 breadth to sustain the calculated load of 306-533 cwts ? 



In this case the formula is No. 3 of the values of b, and by substitution, 

 we get 



, Iw 36 X 306-533 „ . , 



o = = ■- ^ = 3 inches. 



r(,d- 



7-6 X 22-" 



Erample 3. Let the length and the breadth remain, what must be the 

 depth to sustain the calculated load of 30C-533 cwts ? 



Here the formula is No. 3 in the values of (/, and by substitution we obtain 



'=\/lTb-^\/- 



36 X 306-533 



7-6 X 3 



= 22 inches. 



And exactly in the same manner may the strength, breadth and depth be 

 calculated for any other case, observing alw-ays to employ the constant which 

 is adapted to that particidar case. 



Example 4. A cast iron beam of which the transverse section is an open 

 rectangle (fig. 2), is supported horizontally on two props 36 feet apart ; what 

 load will tlie beam sustain when equally ditfused throughout its length, the 

 breadth being 3 inches, the whole depth 22 inches, the depth of the open 

 part seven-tenths of the whole depth, and the specific gravity 7-372 ? 



The formula for resolving this example is No. 4 of the compartment for 

 open beams, where we have 



_ lJ-2&d-(l-y) 15-2x3x22- (l--7^) 15-2 x 3 x 484 x -65 ; 



"'~ I ~ 36 " 36 ~ 



402-7848. 



The breadth and depth to bear the given load, may respectively be found 

 as in the preceding case. 



Example 5. A cast iron beam of the grooved or double flanged section (fig. 

 3), has its extremities fixed into solid walls which are 36 feet apart ; what 

 must be its depth to support a load of 928 cwts. at the middle of its leugth, 

 the whole breadth being 6 inches, the lesser or middle breadth three-eighths 

 of the whole breadth, and the depth of the middle part or that between the 

 flanges three-fourths of the whole depth ? 



The formula for this example is No. 5 of the value of d, for the grooved or 

 double flanged section, from which we have, y = l — f = | = -625, and /( = -75, 

 and therefore it is 



\\\-ib{\-qpfJ \ll-4: 



36 X 928 



6 (1--620 X 



■rof)" 



^254 



and consequemly, the depth between the flanges is 25-75 x -75 = 19-3125 or 

 19.j% inches. 



Example 6. The whole breadth of a feathered or single flanged beam is 8 

 inches, the lesser breadth 2 inches, the lesser depth f of the whole depth, 

 and the length 36 feet ; what must be the whole depth so that it may sup- 

 port a load of 1200 cwts. uniformly distributed over the length, supposing 

 both its ends to he fixed as in the last example ? 



The formula for this case is No. 6 of the values of <?, for the single flanged 



8 — 2 

 er feathered section (fig. 4), from which we have q= - = -75andjo = 



f = -62 5 ; therefore by substitution we get 



91-26 (1-yy 

 36 X 1200 (yi- -75 X -625^+ v'T--75 



Jxl-o) J 



'l--75x-625^+ v'l--75;- i _|_ 

 1--75X -625^ X 1---5) J 



^23-903 inches, 



\ 91-26 (1--75X -625^ X 1---5) 



nd consequently the lesser depth is 23-903 x -625 = 1494 inches. 



From what has been done above, the mode of reducing the cases for the 

 other sections will become manifest, and since our limits will not permit us 

 to enter at large into the subject, the subsequent Uhistrations must be left 

 for exercise to the reader. 



RAILWAY BILL. 

 The Boaril of Trade has opened the campaign against the engineer- 

 ing interests, and we fear with better success than ever. Last year 

 they were defeated on the Steam Navigation Bill, and obtained a par- 

 tial success on the Railway Act, but by the mere passing of this mea- 

 sure, trivial as it was in itself, they have got the point of the wedge 

 in, and are preparing to drive it home. Fortune has worked well for 

 them in the interim, a series of lamentable accidents continued almost 

 uninterruptedly during the recess, and the government borne on the 

 full tide of public alarm and interested exaggeration, sail on to com- 

 plete their victory. We attribute their success both last year and 

 this, for we fear that it is already certain, to the inefficient manner in 

 which the opposition was conducted, if indeed that could be called 

 opposition which was to a great degree suicidal assistance. It is true 

 the railway press thundered, but the great division aiiiong the railway 

 interests prevented any effective combination, while officious indivi- 

 duals, anxious to show their importance by any kind of meddling, had 

 full opportunity of deluding the ministers as to the feelings of the 

 companies, and of being deluded themselves. We ourselves in tliis 

 might have been in some degree to blame that we were satisfied with 

 leaving the matter in the hands of the directors, and that we did not 

 enforce that there were other interests also concerned, the representa- 

 tion of which could not fairly be trusted to a body having enough to do 

 to defend themselves. It was a parallel case to the steam navigation 

 bill, and had we clone rightly we ought at once to have seen the course 

 which it was our duty to have adopted. We felt that in the one case 

 the steam-boat owners would neglect the interests of the marine engi- 

 neers, and we aroused that branch of the profession to the necessity of 

 uniting and protecting themselves, co-operating with the steam-boat 

 owners in their opposition to the general principles of the bill, and 

 keeping a watchful eye upon whatever was calculated to affect them- 

 selves in particular. A similar course of proceeding it now becomes 

 incumbent upon us to urge in the present instance, the railway direc- 

 tors are absolutely insensible to the dangers which menace themselves, 

 so that it is worse than useless to expect that they will afford any 

 protection to those much more menaced — the engineers. We have 

 seen the disposition to interfere with the due exercise of the profes- 

 sion manifested in the steam navigation bill, and we see it still further 

 developed in the report of the railway commissioners to the Board of 

 Trade. In this report the engineers may find what is in store for 

 them. 



With regard to the nature and extent of these powers, the proper distinc- 

 tion appears to us to be that the Government should not attempt to interfere 

 in questions of an experimental nature, which are still subjects of discussion, 

 and admit of a fair difl'erence of opmion among practical men ; nor shotild it 

 attempt to regulate matters of detail, so as to take the management of the 

 railways out of the hands of the parties immediately rebjiousible, viz., the 

 Directors and their officers. 



On the other band, the Government shotUd have the power of enforcing, 

 whenever it is foimd necessary, the observance of all precautious and regula- 

 tions which are approved by experince, and are obviously conducive to the 

 public safety. For instance, upon such points as the comparative advantages 

 of six and four-wheeled engines, the best construction and mode of laying 

 down rails, the best form and construction of wheels, axles, &c., and other 

 points of a similar nature, upon which the practice of the best conducted 

 railways differs, and the opinion of the most eminent engineers is by no means 

 decided, it would be premature for the Government to interfere until experi- 

 ence has solved the questions which mav still be fairly considered as doubt- 

 ful. 



Here we have an admission that although government do not now 

 interfere, they reserve the right of " doing so at a future period, and 

 they claim the power of introducing upon all railways, whatever has 

 been adopted and proved to be conducive to safetv by the practice of 

 those which are considered to be the best conducted." Proved! what 

 has been proved in these days of invention and innovation, has the 

 stage coach been proved i has the sailing vessel ? has timber been 

 proved to be the best material for ships ? What has been proved to 

 be perfect, or impossible to be superseded ? and the Board of Trade 

 would come forward and deprive the engineer of the freedom of com- 

 petition. Would commissioners, advocates of the fifty-six inch gauge, 

 have allowed the broad gauge and all the consequences attendant on 

 it, or would they have been satisfied with what had been adopted and 

 approved upon the best conducted railways ? Would turnpike road 







