"it cannot be brought to perfection without the strong heat of the sun"; and all recorded experience indicates the great importance of slow drying of the varnish under suitable conditions. Stradivari himself wrote to account for delay in the delivery of an instrument because of the time required for the drying of the varnish.
That a perfect varnish conduces to the preservation of a fine tone in the instrument is generally admitted; and its operation in this respect is due, not merely to the external protection of the wood from deterioration, but especially to its action, when supplied under favourable conditions to wood at a ripe stage of seasoning (when that process has proceeded far enough, but not so far as to allow the fibres to become brittle), in soaking into the pores of the wood and preserving its elasticity. This being so, successful varnishing will be seen to be an operation of great delicacy, and one in which the old masters found full scope for their skill and large experience. The effects, upon the vibrational qualities of the wood, of thickness of coat, texture and gradual absorption into the pores of the wood under favourable conditions of drying, are great and far-reaching, as is proved in the survival through two centuries of the great qualities of the specimens most fittingly treated in this respect.
After the early part of the 18th century the use of the fine oil varnish employed by the great makers was gradually abandoned, concurrently with the decline of the instrument maker's art in Italy. Except in the hands of the fast-diminishing band of craftsmen trained in the old traditions, its place was taken by the newer spirit varnishes which, with their quick-drying qualities and ease of application, satisfied the requirements of the more cheaply manufactured instruments of the period following the death of Stradivari; and before the end of the century these inferior varnishes had quite supplanted the old recipes.
Having regard to all these considerations it is not unreasonable to conclude that the varnish of the old instruments contributed probably the most important single element of thair superiority in tone to their more modern copies. It must, however, be borne in mind that the instrument makers of the 16th and 17th centuries carried on a great and flourishing and a highly developed craft; and that their best creations owe their distinction largely to causes similar to those which produced the great art works of the same period. The violin makers had a lifelong training in their craft. The productions of the famous among them were eagerly sought after. Throughout western Europe the highest in the land were true amateurs of music, and vied with one another to secure the masterpieces of Brescia and Cremona. In such circumstances the trained judgment and wide experience of the craftsman were naturally concentrated upon securing the preliminary conditions of high excellence in his work: the choice of sound and handsome wood; perfection of design and workmanship; the composition of his varnish, and the utmost care and skill in applying it under the best conditions; and, not least important, time for deliberate and thoughtful production. The masterpieces of that period were not constructed upon any exact or scientific system, but were the products of development of a traditional craft working on empirical lines. Such theories of their construction as have been propounded are based on analysis of an already perfected organism; and careful historical research has revealed no record or trace of laws or rules by which the great makers worked.
Elaborate attempts have been made, notably by Savart early in the 19th century, to educe from experiments on the elasticities and vibration periods of various specimens of wood used in some of the older instrument's an exact system for the adjustment of these factors to the production of the best results; but data obtained by experiments with test specimens of regular shape do not carry us very far when applied to so complex and irregular a structure as the violin. The vibrating plates of the violin are neither symmetrical nor uniform in dimensions. They are not free plates, but are fixed round the whole edge of a very irregular outline; and these conditions, taken together with their unsymmetrically arched form, held under pressure by the tension of the strings, establish a state of complex stresses under vibration which have so far escaped analysis. Their vibratory movements are moreover influenced by so many accessory features of the instrument, such as the bass-bar, already described, the reaction of the sound-post, and the different pressures by the two feet of the bridge, that it is impossible to figure closely the vibrations of any given area of the instrument. It is certainly very remarkable that so precise a pattern of irregular form should nave been arrived at empirically, and should have survived as the standard, apparently for all time. Not only is the arch of the plates unsymmetrical in its longitudinal section, but, as is less commonly noticed, the upper bouts, especially in violins of the Cremona school, are slightly shallower than the lower; so that the edges of the belly are not strictly parallel to those of the back, but the two plates converge in the direction of the head. Probably the most successful attempts at analysing the vibrations of the violin have been those made by Sir William Huggins, by means of direct tactile observation with the finger holding a small rod of soft wood upon various spots on the surface of the vibrating plates. By this method he made a number of observations partially confirming, and in part correcting the determinations of previous investigators. He found that the position of maximum vibration of the belly is close to the foot of the bridge, under the fourth string, while that of least vibration is exactly over the top of the sound-post. The back, which is strongly agitated, also has its point of least vibration where the sound-post rests upon it. With the sound-post removed the belly vibrated almost equally on both sides of its area, while the vibration of the back was very feeble, and the tone became very poor; supporting the view that in the complete instrument the vibrations of the back are derived from the belly mainly through the sound-post. Pressure on that point in the belly normally in contact with the top of the sound-pest partially restored the proper character though not the power of the tone; indicating the important function of the sound-post in establishing a nodal point which largely determines the normal vibration of the belly. Modifications of the material of which the sound-post was made produced a profound effect upon the quality, but comparatively small effect upon the power of the tone. Of the part played by the sides in transmitting vibrations from belly to back, the most important share is borne by the middle bouts, or incurved sides at the waist of the instrument.
Experiments made lately afford some interesting evidence as to the nature of the vibrations set up in a sounding-box in response to those of a string at various pitches and under various conditions of bowing. These observations were made on a monochord and restricted to one portion of a sounding-board of regular shape. Experiments on similar lines made with an actual violin body might throw further light upon the behaviour of that instrument as a resonator; but such researches entail prolonged investigation.
Two phenomena, familiar to violin players, are suggestive of further lines of research that may help to elucidate the problems of the localization of the principal responses in the body of the violin, and of the action of the wood under vibration. Many violins, especially old and inferior ones, fail to resonate clearly and fully to particular notes, the sounds produced being commonly known as “Wolf” notes; and these notes are, certainly sometimes and possibly always, associated with particular spots in the body of the instrument; for, if pressure be applied at these spots, the resonance of the respective “Wolf” notes is improved. This observation suggests that the region concerned has been cut, or has become disproportionately thin in relation to the normal thickness of the plate; and, when stimulated by the appropriate note, sets up a local system of vibrations, which interfere with, instead of sharing, the proper vibrations of the plate as a whole; this interfering vibration being damped by local pressure. These defects are said to develop with age and constant use, and to be minimized by the use of thin strings but aggravated by thick ones; a circumstance which tends to support the hypothesis of thin regions in the plate, which might be expected to respond more truly to the vibrations of lighter, than to those of heavier strings. Detailed investigation of these phenomena on the lines of the experiments already referred to may have valuable results. Another well-known characteristic of the violin is that a new instrument, or one that has been long in disuse, is found to be "sleepy," that is, it fails to speak readily in response to the bow, a defect which gradually disappears with use. Experiments made to test the effect of prolonged transverse vibrations upon strips of suitable wood have shown that such treatment increases the flexibility of the wood, which returns to its normal degree of rigidity after a period of rest. No conclusive interpretation of these experiments has yet been offered; but they indicate the probability of modifications of the internal viscosity of the wood, by molecular changes under the influence of continued vibratory movement.
The function of the bridge, as above mentioned, is to communicate the vibrations of the strings to the resonating body of the violin. This communication is made mainly, though not entirely, through the left foot of the bridge, which under the comparatively low tension of the G string rests with light pressure upon the belly, which at that point has accordingly greater freedom of movement than under the other foot, in proximity to which the sound-post, extending from back to belly, maintains that region of the plates in a state of relative rigidity, under the high tension of the E string. The view, however, maintained by some writers that the right foot of the bridge communicates no vibrations directly to the belly is inaccurate. The main object of placing the sound-post some distance behind, instead of immediately under, the bridge foot is to allow the belly under that foot to vibrate with some freedom. This has been proved by the destructive effect produced upon the tone by fixing the sound-post immediately under the foot of the bridge.
The form into which the bridge is fretted after the pattern devised by Stradivari has given rise to some speculation; but the justification of this form is probably to be found in the explanation propounded by Sir William Huggins, namely, that the strings, when agitated by the bow, vibrate in a plane oblique to the vertical axis of the bridge; the vibrations may be accordingly resolved into two components, one horizontal along the length of the bridge, the other vertical — that is, in a direction favourable for setting the belly into vibration across its lines of support.
It is advantageous to maintain simplicity in direction of the vibrations communicated to the body, and therefore to eliminate
