Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/147

 Fes. 16, 1872. THE BUILDING NEWS. 151 _ of these trusses are readily calculated in accordance with the principles already explained, with these exceptions, the reasons for which will appear further on. The pillars composing the upper chord are to be ealculated for a length 1, and the weight of each of these pillars, as well as that of each of the upright end pillars, is to be taken at half the weight of a pillar of double its strength. The absence of ties in the central panel at 1 need not embarrass the reader. The weight of that panel is sustained in precisely the same manner as the weight at C in 2. Now suppose these two trusses to be united into one as shown at 3, each pair of top chords, each pair of bottom chords, and each pair of end pillars being consolidated into one, Each of the several members in the compound truss bears the same strain as the corresponding member or members in the simple trusses. We can now compare these strains with those in the simple truss 4, of the same length, the same height, the same number of panels, and bearing the same weights. It will be noticed, first, that each upright pillar in 4, except the end ones, bears sometimes over twice as much as the corresponding pillar in 3; the por- tion of the weight on each pillar which arises from the weight of other pillars being more than twice as great in 4 as in 3. Any tie, as GK’ in 4, bears more than twice the weight of the corresponding tie GM’ in 3; but the tie GM’, acting at a greater angle with the vertical, will be under more than a corre- sponding strain. The strains on GK’ in 4, and GM!’ in 3, are respectively proportional to the weight sustained by each tie multiplied by its length. The quantity of metal in each of these ties is respectively proportional to the tension multiplied by the length. It is therefore proportional to the weight sustained ‘multiplied by the square of the length. That is, supposing GK’ to bear twice the weight of GM.' Weight of GM _ GM? _ i + 40 Weight of GK? °GK2 “RhR+?P For the case of h = 21, this expression becomes 4 ia = 0°80, or the weight of GM’ would be 0-8 that of GK’. The end pillars and ties in 3 and and 4 each support half the truss and load. The advantage, however, is in favour of 3, since that truss is somewhat lighter than 4. The top and bottom chords in 3 will be somewhat lighter than in 4 for the same reason. It is evident that the strains in a truss with double intersections may be calculated, with refer- ence to a partial aS well as a uniform load, by separating it into two simple trusses. In an entirely similar manner we may find the strains in a truss in which the sloping member passes over more than two panels. The preceding examination shows an apparent advantage in the system of multiple intersections, It is only apparent, however, since it involves an assumption whose realisation cannot be assured in practice—namely, the assumption that the maximum load with reference to which the truss is propor- tioned will always rest equally upon each of the simple trusses. In a railway bridge, for instance, it is impossible to be certain that the heaviest trains will not sometimes be composed of cars of such length and distance between trucks, that the weight will rest wholly or in great part upon a single system of ties. To give due weight to this fact it would be necessary to make each elementary truss much more capable of sustaining one-half, one, third, &c., of the assumed load with suitable margin of security. Similar remarks apply in the ease of carriage bridges, and, giving due considera- tion to this point, it does not appear to me that there is any advantage in the system of multiple qntersections. —_—_»—__ STAINED GLASS: ITS APPLICATION TO DOMESTIC ARCHITECTURE.* (Concluded from page 120.) N the majority of houses very rich glass would be as out of place as a fresco would be. But just as we may hang oil-paintings in our rooms without destroying their effect (though it is not often done, by-the-bye) so we may sometimes find occasion for richer glass in the windows, only (as for most oil paintings) we want larger rooms than ordinary. For our first consideration should be that the effect of our window be as perfect as we can make it from that point of view from which we are most likely to see it oftenest. And in a small room it is impossible that we can ever—if we try—get far enough away from it to appreciate a richly-coloured window. Friday, January 26, by Mr. Lewis F. Day. What we see is only a jumble of paint and leads, bars and soldering—an effect of wgliness instead of beauty. The unsightliness of the lead lines and sol- dering may sometimes be obviated by gilding the leadwork, as, for example, where they form the basis of a geometrical design. A study, if it were large enough, and not too dark already, would be just the place for rich stained-glass. No outside scenes or passing objects could obtrude themselves through it to distract your attention, and even of the daylight only such rays would be ad- mitted as were harmonious and mellow—such as would soothe your thoughts and put you in tune with your author. In all stained-glass, but espe- cially in coloured work, good glass is more than half the battle. The best design will look poor and mean if executed on poor thin glass, while the most thoughtless muddle of good glass may produce the most beautiful effects. Witness many of the glorious old windows, that are nothing more than an accidental and unintelligible collection of scraps. If you have thin glass it may be helped by diaper- ing and stronger painting throughout, but nothing can give it the richness of good glass. While on the subject of colour, I must protest against theories of colowr. Imprimis, all theories of colour (and probably all theories) are scientific playthings, from an artist's point of view. No doubt colour is a legitimate subject for scientific inquiry, but, as far as art is concerned, colour is purely a matter of feeling. A man who has no feeling for colour may perhaps be taught to avoid violent discords, but he will certainly never produce fine colour, though he had all the theories of colour at his fingers’ ends. A colourist disposes his colours not a bit from conscious reasons, but just as he fee/s that such and such a colour is wanted just where he puts it. To be suc- cessful in the design of stained-glass windows one must of course especially study, not only the optical effects produced by the juxtaposition of various colours, but also those resulting from the transmis- sion of the light through glass of divers colours, But it is no use to arrive at a scientific knowledge of the laws which govern these effects. No coloured win- dow worth looking at was ever yet produced upon principle. A designer’s experience will tell him that certain reds and blues, in certain proportions, will run together into a purple; that certain greens and blues will tell well together; that the effect of yellow may be much more golden in his glass than he can get it in his drawing; that white, and colours approaching to it, will spread unduly; and so on; and if he will only take his experience for his guide he need not trouble himself about theories. We may be taught, on high authority, that a perfect scheme must contain a due proportion of colour— that is, the proportion of 3 of yellow, 5 of red, and 8 of blue, a ray of white light being supposed to con- sist of the three primary colours in those proportions, But though the hint that blue should preponderate, and yellow be least in proportion in a coloured com- position, might be useful to a novice, all theories based upon chromatic tables of proportion are as impracticable as they are arbitrary. Good colour cannot be described ; it is a test of good colour that you don’t quite know what to call it, and in attempt- ing to describe it you hesitate between two or three colours, and finally have to incorporate an example in your definition, such as “a greenish twrquoise- blue,” “a yellow brown olive-green,” “a warm reddish apricot-yellow.” But only such gross crude positive colours as can be exactly defined come within the palette of the theorist; he is debarred- from the use of the subtler and more delicate colours by his theory. Whatever may be the proportion of the primaries in a ray of white light—whether there be three of them, or two (as has recently been asserted), or seven (as used to be believed), Dame Nature, with an eye for colour, has discreetly and kindly concealed the fact from us. We may analyse white light, but no spectroscope, no chemical analysis, will enable us to arrive at a patent recipe for colour. It might be convenient if we had it allsettled for us: “Take 3 of yellow, 5 of red, and 8 of blue; distribute over a geometric basis (taking care that the junction of curved lines be tangential, and that no two colours impinge), sugar with Orientalism, flavour with taste at dis- cretion, and serve up in the form of art.” But how is a man to arrive at a pure red, blue, and yellow (even if it were desirable he should do so)? And then how is he to measure his 3 parts of one and his § of another? He must trust to his eye after all. Better far, then, trust to his eye altogether, and not hang a theory round his neck to clog him in the race of success. The theorist, again, will often argue learnedly on the optical result of light passing through glass of various colours, but I don’t believe that any glass-painter will ever profit by his re- searches. There are two systems upon which we can pro- ceed in designing for glass. The one is to block out your design with the lead lines, as it were, and develope it by the painted detail. This is the more strictly mosaic system, of which the Early English work is an example. The other is to first sketch out your painted design and then strengthen the out- line by the addition of the leads. This is rather the method on which the later Gothic glass-painters went to work. The former of these methods is the more orthodox, but both are admissible, though neither of them will be sufficient, unless in designing upon the one plan we bear in mind the other—that is to say, in blocking out our design in lead lines, we must remember thatit has to be supplemented with painted details ; and in sketching out our subject in the more pictorial manner we must not for a moment forget that it has ultimately to submit to lead lines. The first condition of success in design is to be quite clear as to what it is we have to do. What is it that we purpose in glass-painting? Our prime object is to modify, subdue, and soften the harsh, raw day- light, or in domestic work, to shut usin (as I have said) from outside ugliness and observation. In effecting this the opportunity occurs of introducing more or less richness and harmony of colour, of which we should be foolish not to avail ourselves so long as they do not interfere with our convenience, or with the wholeness and consistency of the archi- tectural effect, attracting no more than their due at- tention. Further, it is desirable that this beauty of colour should not be altogether meaningless, but should, on closer study, prove to enshrine the utmost beauty of design, idea, and execution. And over and above these characteristics, itis necessary, to the perfec- tion of our work, that the drawing should be the very best that is practicable, not always intrinsically the best; the artist must be restrained, not by want of artistic knowledge, but by the technical knowledge of the object he has in view, and of the means to that end. It is worse than waste of time and ability to draw forms that cannot be cut entire, and that must therefore be marred by leads in unseemly places, or that must be disfigured by the intersection of un- sightly bars, when a slight modification’ of the forms would have sufficed to convert these ugly necessities into elements of possible enrichment. ““We know very well that there are plenty of artists of our day whose ideas are much too independent to submit to any law but that dictated by their own un- ruly fancy ; but we also know (and not less certainly) that the laws which govern light, optics, and per- spective have not yet modified their action to please these lawless spirits.” Between the two follies of an affectation of the archaic art of the earliest glass painters, and the modern (not to say childish) faney for coloured pictures in glass, it is wonderful that the art of glass-painting has not quite fallen to the greund. I think I shall carry you with me when I say that it is of no use flying in the face of our materials. What we have to do is to understand them thoroughly, and then we can do what we like with them; they are all on our side then. Good glass is honest glass. There must be no shirking the inevitable conditions of our materials, but they must all be made the most of. The bars must be accepted as such; the leadwork must acknowledge itself as glazing; the painting must bear evidence that itis brushwork; the glass must glory in its translucency ; the whole must confess itself a window, and a window “Built by the only law, that use be suggestive of beauty ; Nothing concealed that is done, but all things done ta adornment : Meanest utilities seized as occasions to grace and embellish.” It may appear that I have been dogmatising to a considerable extent, and laying down arbitrary laws which perhaps do not apply to some of the best work that has been done. I wish to disclaim the inten- tion at least of laying down any definite and rigid laws for the glass painter. Good and experienced workmen follow a code of their own (although, per- haps, they could not write it down for you), and a master can do what he likes, and invariably proves his mastery over his materials by succeeding in the teeth of all the laws that have ever been laid down. But for beginners some sort of grammar is not wholly unnecessary, and I have endeavoured to throw out a few hints that may assist them in their study of stained ¢ However my manner may have seemed to belie it, I speak in the character of a student, and if I have presumed, it is only in the presumption that I have devoted probably more con- sideration to the subject than the majority of my fellow students here. At the same time, I am aware that there are (or may be), many present who have had opportunities of studying the subject longer than I have, and who have possibly arrived at very different conclusions to myself.
 * Paper read before the Architectural Association on