A few words as to the thickness of the upper and lower tables. Of this much has been written, an extremely small portion being from actual observation, and most of the other parts being reiterated assertions started many years back by people whose supposed knowledge rested solely upon simple conviction, without an iota of _bona fide_ evidence in support. To them the fact, well known to everyone engaged in the manufacture of sound-boards of musical instruments, that a very thick sound-board produces different results to that of a very thin one, was sufficient, therefore the secret of Stradivari with regard to his tone, was "the adjustment of the thicknesses," whatever that may mean. The assertion seeming perhaps rather bare, and wanting some sort of support, was bolstered up with another no less instructive, that if you "pinged," or tapped the separated upper and lower tables of a Stradivari so that they each gave out a note there would be found the difference of a tone between them! Here was something for the "babes and sucklings" of the craft of violin making to swallow. It was stated also which table would give the higher tone. Unfortunately for some would-be Stradivaris, the particulars of the tonal difference were copied loosely and reversed and so came "confusion worse confounded." The illustrations of sound holes, or _f f_ commonly so called, will, it is hoped, be interesting as showing the modification or development from those of Nicolas Amati to the latter part of the period of Stradivari's career, called "the grand." They are all reproduced from fine specimens of the great Cremonese masters, and are the exact size of the originals. The first (_a_) shows the _f_ of a violin of the Nicolas Amati's late period, 1663, unaffected--at least in this detail--by the individuality of his hereafter eminent pupil. (_b_) While still going under the name of Nicolas Amati, 1678, the _f_ shows the actual interference of Stradivari, it is more vertical, but the peculiarities of the upper and lower wings are retained. (_c_) 1684. The design is quite changed, there is some return to the flow or inclination of Amati, but the whole thing is more extended, is slender, and the upper and lower wings are widened, this modification was retained for a permanency. (_d_) 1690. There is some return to the vertical design, but the width of the wings is retained, while the lower part of the design is of larger proportions. (_e_) 1700. The design is more equalised and is more substantial. (_f_) 1715. The same proportions are kept with an increase of gracefulness. It will be perceived the lower wing approaches at its lowest part the opposing curve more closely, the upper one likewise; in some specimens of this period it is still closer. (_g_) 1725. While the upper part is very like the preceding, the lower part is more contracted and curled up. There is a somewhat