**DOUBLE**: two of a sort, one corresponding to the other.

**Double Children, Double Cats, &c.** See MONSTER.

**Double Employment**, in Music, a name given by Rameau to the two different modes in which the chord of the sub-dominant may be regarded and treated; namely, as the fundamental chord of the sixth superadded, or as the chord of the great sixth, inverted from a fundamental chord of the seventh. In reality the chords carry exactly the same notes, are figured in the same manner, and are employed upon the same chord of the tone, in such a manner that frequently we cannot discern which of the two chords the author employs, except by the assistance of the subsequent chord, which resolves it, and which is different in these different cases.

To make this distinction, we must consider the diatonic progress of the two notes which form the fifth and the sixth, and which, constituting between them the interval of a second, must one or the other constitute the dissonance of the chord. Now this progress is determined by the motion of the bass. Of these two notes, then, if the superior be the dissonance, it will rise by one gradation into the subsequent chord, the lower note will keep its place, and the higher note will be a superadded sixth. If the lower be the dissonance, it will descend into the subsequent chord, the higher will remain in its place, and the chord will be that of the great sixth.

With respect to the composer, the use which he may make of the double employment is to consider the chord in its different points of view, that he may thence know how to make his entrance to it, and his exit from it; so that having, for instance, arrived at the chord of the superadded sixth, he may resolve it as a chord of the great sixth, and reciprocally.

D'Alembert has shown that one of the chief uses of the double employment is, that we may be able to carry the diatonic succession of the gamut even to an octave, without changing the mode, at least whilst we rise; for in descending we must change it. Of this gamut, and its fundamental bass, an example will be found in Rousseau's Musical Dictionary. It is evident, according to the system of Rameau, that all the harmonic successions which result from it are in the same tone; for, in strictness, no other chords are there employed but three, namely, that of the tonic, that of the dominant, and that of the sub-dominant; which last, in the double employment, constitutes the seventh from the second note, and is employed upon the sixth.

With respect to what D'Alembert says in his Elements of Music (p. 70), and repeats in the Encyclopédie (article Double Employ), that the chord of the seventh re fa la ut, though we should even regard it only as an inversion of fa la ut re, cannot be followed by the chord ut mi sol ut, Rousseau declares, "I cannot be of his opinion in this point." The proof which he gives in support of this dissent is, that the dissonance ut of the first cannot be resolved in the second. And this is true, since it remains in its place; but in the chord of the seventh, re fa la ut, inverted from the chord of the superadded sixth, fa la ut re, it is not the ut, but the re, which is the dissonance; and consequently it ought to be resolved in ascending upon mi, as it really does in the subsequent chord; so that this procedure in the bass itself is forced, which, from re, cannot without an error return to ut, but ought to ascend to mi, in order to resolve the dissonance.

D'Alembert afterwards shows that this chord re fa la ut, when preceded and followed by that of the tonic, cannot be authorized by the double employment; and this is likewise true; because, in fact, this chord, though figured with 7, is not treated as a chord of the seventh, neither when we make our entrance to it nor our exit from it; or at least that it is not necessary to treat it as such, but simply as an inversion of the superadded sixth, of which the dissonance is the bass; in which case we ought by no means to forget that this dissonance is never prepared. Thus, though in such a transition the double employment is not in question, and though the chord of the seventh be no more than apparent, and impossible to be resolved by the rules, this does not hinder the transition from being proper and regular. This inversion of the chord of the sixth superadded, which transfers the dissonance to the bass, has been censured by Rameau, who, taking it for a fundamental chord, the chord of the seventh, which results from it, rather chose to make the fundamental bass descend diatonically, and resolve one seventh by another, than to unfold this seventh by an inversion. But Rousseau has dissipated this error, and many others, in some papers which long ago passed into the hands of D'Alembert when he was composing his *Elements of Music*. In other respects, the double employment cannot be used with too much reserve, and the greatest masters are the most temperate in putting it in practice.

**Double Fiché**, or *Fiché*, in Heraldry, the denomination of a cross, when the extremity has two points; in contradistinction to *fiché*, where the extremity is sharpened away to one point.

**Double Octave**, in Music, an interval composed of fifteen notes in diatonic progression, and which, for that reason, is called a *fifteenth*. It is, says Rousseau, an interval composed of two octaves, called by the Greeks, *disposition*.

It deserves, however, to be remarked, that in intervals less distant and compounded, as in the third, the fifth, the simple octaves, and so on, the lowest and highest extremes are included in the number from whence the interval takes its name. But, in the double octave, when termed a fifteenth, the simple number of which it is composed gives the name. This is by no means analogical, and may occasion some confusion. We should rather choose, therefore, to run any hazard which might occur from uniformly including all the terms of which the component intervals consist, and call the double octave a sixteenth, according to the general analogy.

**Doublet**, among lapidaries, implies a counterfeit stone, composed of two pieces of crystal, and sometimes glass softened, together with proper colours between them; so that they make the same appearance to the eye as if the whole substance of the crystal had been tinged with these colours.

The impracticability of imparting tinges to the body of crystals, while in their proper and natural state, and the softness of glass, which renders ornaments made of it greatly inferior in wear to crystal, offer inducements to the introduction of colouring the surface of crystal wrought in a proper form, in such a manner that the surfaces of two pieces so coloured being laid together, the effect may appear the same as if the whole surface of the crystal had been coloured. The crystals, and sometimes white transparent glass so treated, were called *doublets*, and at one time prevailed greatly in use, on account of the advantages with respect to wear which such doublets had, when made of crystal, over glass, and the brightness of the colours which could with certainty be given to counterfeit stones in this way, when coloured glass could not be procured, or at least not without a much greater expense. Doublets have not indeed the property which the others have, of bearing to be set transparent, as is frequently required in drops of ear-rings and other ornaments; but when mounted in rings, or used in such a manner that the sides of the pieces where the joint is made cannot be inspected, they have, when formed of crystal, the title to a preference over the coloured glass; and the art of managing them is therefore, in some degree, of the same importance with that of preparing glass for counterfeiting gems, and is properly an appendage to it, as being entirely subservient to the same intention. The manner of making doublets may be shortly described.

Let the crystal or glass be first cut by the lapidaries in the manner of a brilliant, except that, in this case, the figure must be composed of two separate stones, or parts Doublets of stones, formed in the manner of the upper and under parts of a brilliant, if it was divided into a horizontal direction, a little lower than the middle. After the two plates of the intended stone are thus cut, and fitted so exactly that no division can appear when they are laid together, the upper part must be polished ready for setting; and then the colour must be put betwixt the two plates by the following method. Take of Venice or Cyprus turpentine two scruples; and add to it one scruple of the grains of mastick chosen perfectly pure, free from foulness, and previously powdered. Melt them together in a small silver or brass spoon, ladle, or other vessel, and add to them gradually any of the coloured substances mentioned below, but well powdered; stirring them together as the colour is put in, that they may be thoroughly mixed. Then warm the doublets to the same degree of heat as the melted mixture; paint the surface of the lower part, and put the upper one instantly upon it, pressing them to each other, but taking care that they may be conjoined in the most perfectly even manner. When the cement or paint is quite cold and set, the redundant part of it, which has been pressed out of the joint of the two pieces, should be gently scraped off the side, till there be no appearance of any colour on the outside of the doublets; and they should then be skilfully set; observing to carry the mounting over the joint, that the upper piece may be well secured from separating from the under one.

The colour of the ruby may be best imitated by mixing a fourth part of carmine with some of the finest crimson lake that can be procured. The sapphires may be counterfeited with very bright Prussian blue, mixed with a little crimson lake, to give it a cast of the purple. The Prussian blue should not be very deeply coloured, or but little of it should be used, otherwise it will give a black shade that will be injurious to the lustre of the doublets. The emerald may be well counterfeited with distilled verdigris, to which is added a little powdered aloes. But the mixture should not be strongly heated, or kept long over the fire after the verdigris has been added. The resemblance of the garnet may be made with dragon's blood; which, if it cannot be procured of sufficient brightness, may be helped by a very small quantity of carmine. The amethyst may be imitated with the mixture of some Prussian blue with the crimson lake; but the proportions can only be regulated by direction, as different parcels of the lake and Prussian blue vary extremely in the degree of strength of the colour. The yellow topazes may be counterfeited by mixing the powdered aloes with a little dragon's blood, or by good Spanish arnotta; but the colour must be very sparingly used, or the tinge will be too strong for the appearance of that stone. The chrysolite, hyacinth, vinegar garnet, aqua-marine, and other such weaker or more diluted colours, may be formed in the same manner, by lessening the proportions of the colours, or by compounding them together corresponding to the hue of the stone to be imitated; for which purpose it is proper to have an original stone, or an exact imitation of one, at hand when the mixture is made, in order to adapt the colours to the effect desired.

There is an easy method of distinguishing doublets, which is only to behold them betwixt the eye and light, in such a position that the light may pass through the upper part and corners of the stone; when it will easily be perceived that there is no colour in the body of the stone.

**Doublets**, a game on dice within tables. The men, fifteen in number, are placed thus: Upon the six, cinque, and quatre points, there stand three men a piece; and upon the trey, deuce, and ace, only two. He who throws Doubling highest has the benefit of throwing first, and what he throws he lays down, and so does the other; what the one throws and has not, the other lays down for him, but on his own account; and thus they proceed until all the men are down, and then they hear, as it is called. He who is first down bears first, and will double win the game if the other throws not doublets to overtake him; which he is sure to do, since he advances or bears as many as the doublets make, namely, eight for two fours.