346 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[October, 



In regard to the plan here shown as tliat for a dining room, it is not 

 proposed as one capable of being strictly followed, because it \vouId 

 stand in need of more or less alteration in order to adapt and adjust 

 it, so as to combine advantageously with the rest. Of course it is here 

 presumed that there is nothing to hinder its being executed precisely 

 as it is represented in the cut. The door near tlie sideboard is sup- 

 posed to open into a corridor communicating with the offices, and the 

 other from a vestibule or ante-room, as the case might be. There are 

 four pedestals for candelabra, and there might be others in the two 

 arches within the recesses : these, however, are not absolutely essen- 

 tial to the design, but might be adopted or omitted according as more 

 or less decoration should be held desirable, — a point to be regulated 

 by the scale of embellishment fixed upon. The recesses and semi- 

 circular ends of the room are supposed to be floored with ornamental 

 tiles or mosaic (like the saloon of tlie Reform Club), and the square or 

 centre part to be covered with a rich c.irpet. Or eise the whole might 

 be carpetted, and the same kind of di^tinction be nevertheless kept up, 

 by putting down plain carpetting of some quiet neutral tint at the ends, 

 for the purpose of giving more importance to the middle compartment 

 of the room, and to the two extreme ones somewhat the air of being 

 spacious semicircular alcoves with smaller recesses within them. 

 After all, however, the propriety of so doing would depend upon 

 whether any corresponding sort of distinction between the several 

 divisions of the room was observed in the design of the ceiling. .Should 

 the situation of the room be such as to admit of the centre being 

 lighted from above, the ceiling might then be raised by a cove, and 

 have a lantern occupying the rest of it. In such case no side windows 

 would be required, still the one at the end of the room might be re- 

 tained, unless it should be preferred to make a second sideboard recess 

 corresponding with that at the opposite end, or to have these folding 

 doors opening from an ante-room, substituting a niche for the present 

 door in the recess on the left hand. 



( To he continued.) 



ON THE FORMS AND PROPORTIONS OF STEAM VESSELS. 



Though reluctant to call in question the opinions of so able a writer 

 as " H. P. H." appears to be, I think he lias no autboritv for multiplv- 

 ing the "sectional ana of the immersed parts" of a steam vessel, into 

 the (mean) dtjjth below the surface of the water, in order to find the 

 resistance to her motion. Doubtless this would be correct for " flood- 

 gates," of which one surface only is exposed to the water, and the 

 pressure is that arising from the might of the fluid ; but the case of 

 a vessel is totally difierent, the resistance arising not from any weight 

 of the fluid, (for the pressure on the after half of the vessel tending to 

 push her forward, is exactly equal to the pressure on the fore part 

 which tends to retard her,) but from a species of friction and from the 

 inertia of the fluid. This resistance probably increases in porportion 

 to the densily of the water, not to its depth. 



As the whole of the theoretical part of the article "On the Forms 

 and Proportions of Steam Vessels," is founded on the presumption 

 that the resistance is proportional to the section and depth, instead of 

 section without regard to depth, as given in mathematical works, and 

 as It will be completely erroneous if the above view is the correct one, 

 It may be worth while for H. P. H. to reconsider the nature of the re- 

 sistance of which he writes, and to favour the readers of the Journal 

 with his opinions — waiting which I am, 



Very respectfully, 



Neath, lUhof^lh month, 1841. 



ON THE STRAIN OF BEAMS. 



Sir— It may be interesting to trace the effects on beams of strains 

 acting on them in a parallel direction. In the common hand punch, 

 lor example there is an upright beam bent at right angles at top to a 

 convenient distance, the extremity being fitted to receive the reaction 

 ot the plates under the punch. Here the strain on the beam is up- 

 ward. Instances of similar downward strains, too, are familiar, as in 

 some portable balances, in which the scales hang from the extremity 

 of an upright standard bent forward at the upper end. 



Let ABC be an upright standard rising perpendicularly from the 

 sole N C. and beut at right angles at B; let it be subjected to a force 



acting downwards in the line A N parallel toBC. Then it would 

 appear on a general view, that the pait BC will be equally affected 

 throughout, as the force, which let AD represent, has the same lever- 

 age on all points of B C. 



But, more particularly, in estimating the action of the force on any 

 point M, we may consider it as acting on M by the imaginary straight 

 lever AM. The action of the force A D on M may be analysed by 

 drawing D F perpendicular to A M ; A D =: A F and F D, the former 

 being longitudinal pressure along A M, the latter, a lateral strain on 

 the cross section at M by the leverage AM. Similar resolutions for 

 other points in BC will form right angled triangles on the common 

 base AD, and thus the locus of the vertices of these triangles is a 

 circle described on the diameter AD, passing through point F, of 

 course. 



To ascertain how the forces A F, F D, acting on the section M, 

 affect any other section, as that at the base C, draw AC cutting the 

 circle at E, join D E, and complete the parallelogram O E ; draw F H 

 perpendicular to O D, cutting A E and O D at L and H. Then A F=i 

 A L and L F, and F D = D H and H F, these four resultants all acting 

 at point A on lever A C ; the sura of the longitudinal strains is A L -|- 

 HD = AL + LE = AE; the lateral strains LF and F H, acting in 

 opposite directions =FH — FL^HL= DE. Thus the resultants 

 of the forces A F, F D, acting on the section M, are A E and E D on 

 section C. But A E and ED are also the resultants of AD acting 

 directly on section C. It appears, then, that the effect of the force 

 AD on the section C is one, whether acting directly by A C, or indi- 

 rectly by AM C. Again, the reciprocal action of the forces A E, E D, 

 acting directly on C, upon the section M, may be had by drawing EK, 

 Eti perpendicular to D F, AM respectively. For we then have 

 D E =: E K and K D, and A E = A G and G E'. Then G E or F K -f 

 K D = F D, and A G — K E or F G = A F. But A F and F D are 

 the resultants of A D acting directly on M. Therefore, as M and C 

 represent every two points in B C, and as the direct action of the 

 force AD on either point is identical with its indirect action through 

 the other point, we conclude, generally, that its action on every cross 

 section of B C is constant, and therefore B C ought to be of equal di- 

 mensions from bottom to top. Draw O P perpendicular to AD, then 

 A0 = AP andPO, and DO = OP and P D, and as PO in these 

 two quantities acts in opposite directions, we have AO and DO = 

 A P and P D =: AD, which intimates that there is no lateral thrust on 

 the standard, so that the cross section of BC may at once be deter- 

 mined from the quantities A D, NC. The part AB ought to have 

 the parabolic outline, modified when the corner B is rounded. 



By supposing all the forces reversed in direction, the above demon- 

 stration will apply also to standards subjected to upward strains. 



I am. Sir, 



Pheenix Iron Works, Your obedient servant, 



Glasgow, 20th ^4ug. Daxiel Clark. 



P. S. I think it would be a great improvement to introduce symbols 

 to express the most common terms in papers of the nature of the pre- 

 ceding: o fi-^r circle, i ior perpendicular, Sic. 



