We may Study Nature upon the Latine it selfe which may serve as well for a model as it doth for a principle; It will in the first place acquaint us that the Vowels are almost accounted for nothing, for altho there are some of them that admitt of easie changes among themselves according as they are more open or reserv'd, we know neverthelesse that there are none of them but what may be absolutely shifted into the place of another of what kind soever, either immediately, or by succession and degrees. For a finall confirmation of this we have no more to doe but to make an easie comparison of the different derivative of the same word, the reference of these three _Cepa_; _incipio_ and _occupo_, to the Verb _Capio_ may serve for an instance, if we shall but grant the truth of this principle which the orientalists have always suppos'd, who form the greatest part of their words from the sole change of their Vowels. The same is not altogether allowable in relation to the Consonants, where we must not admitt indifferently all sorts of changes; the sole affinity of the Organs is that which must regulate almost all their varieties: the Labiall letters easily supplant one another but the Dentall or Linguall with more difficulty succeed them as being not of the same order; For as these consonants, M. B. P. V. F. make neer the same sound, which is modified by the divers force of the Air opening the lips after severall forms. So the Letters D. T. Z. S. ought to make an order by themselves, having a particular relation to the point of the tongue, which only by touching upon the teeth in various manners frames their pronunciation. But it is not a single and easie reflexion, that can absolutely determine whether two letters have resemblance and proportion, because there are some of them that being made up of the movements of severall organs, maybe differently alter'd according to their various resemblances, so the letter H. carrys not only the resemblance of a gutturall as it is pronounc'd by the assistance of the muscles of the throat, but also as an Aspiration besides the regard it hath to the whispers of the tongue, and the 6. Aspirates of the Lips, Teeth, and Palate. However if the precipitance or forwardnesse of any, hath by chance brought into use, other methods of altering sounds, as they have not so certain a foundation in reason, so neither can they be receiv'd within the Compas of this Art, at least being not establisht by a regular and constant analogie.