There remains yet two other Symptoms of the _Voice_, which I have undertaken to explicate, viz. why the _Voice_ sometimes leaps from one _Eighth_ to another; and, as it is rightly said by the Vulgar Expression, that it is broken: and why, when we strive to make our _Voice_ either too sharp, or too flat, it at last plainly faileth us. As to the first, let us consider when and how it cometh to pass; and first, it's what principally happeneth to _Orators_, when they endeavour to lift up their _Voice_ too high, or strongly; but how this cometh to be, _Organ-pipes_, and the _Monochorde_, do teach us, _viz._ when some Impediment interposing, doth divide the _ordinary Sound_ into two; if therefore those parts are equal, either of them is by one _Eighth_ more sharp than the former Sound, neither are they distinguished from one another; but if they prove to be unequally divided, then two _distinct Sounds_ are made at the same time, whereof one is flatter than the ether, and this is commonly called a _broken Voice_: But why our _Voice_ should fail us, when we endeavour to make it more sharp, or more flat than it ought to be, the reason is, because we strive either so to contract the _Cleft_ of the _Wind-pipe_, and to press the _Spout-like Cartilage_, by help of the _Bone of Tongue_, towards the _Epiglott_, that the going forth of the _Voice_, and of the _Breath_, may be precluded, or else, on the contrary, because that the said _Cleft_, through the drawing down of the _Cartilages_, is so much widened, that the departing out of the _Breath_, finds no hinderance. But here I had almost forgot to compare the _more dry_, the _more moist_, the _more solid_, and the _more thin_ Constitution of the _Larynx_, or _Wind-pipe_, which also make very much to the rendering the _Voice_, to be either sharp, or flat. That same humming Noise, which _many flying Insects_ make, not so much by the Wings, (for when they are cut off, the humming still remains) as by a most swift and brisk Motion of certain Muscles, hid in the Cavity of their Breasts, seems to have somewhat of an affinity to the _Voice_; wherefore I desire the Learned to examine, whether those small _Muscles, which are proper to the Cartilages of the Wind-pipe_, cannot perform somewhat like to that. Many more Particulars concerning the _Voice_ might yet further be inquired into, such as, how it is, that every one may be known by his _Voice_? How that _Sound_, which in Singing is called _Quavering_, or _Trilling_, by a peculiarity, is excited, &c, But seeing that these things do not properly respect the nature of the _Voice_, I, for Brevities sake, do omit them. CHAP. II. _Expounding the Nature of the_ Letters, _and the manner how they are formed_.