As for the _Speaking Trumpet_, by which a Voice may be convey'd to a considerable distance, I refer its consideration to that of _Refracted Sounds_, or _Refracted Audition_. Thus much of the Improvements of Hearing, that respect its _Object_, which is _Sound_. 2. The _Organ_ and _Medium_ are to be consider'd. And, 1. The _Organ_, which is the _Ear_, is helpt much by placing it near a Wall (especially at one end of an Arch, the Sound being begotten at the other) or near the Surface of Water, or of the Earth, along which the Sounds are most easily and naturally convey'd, as was before declar'd. And 'tis incredible how far a Sound made upon the Earth (by the trampling of a Troop of Horses, for Example) may be heard in a still Night, if a Man lays his Ear close to the Ground in a large Plain. _Otacousticks_ here come in for helping the _Ear_; which may be so contriv'd (by a right understanding the _Progression of Sounds_, which is the principal thing to be known for the due regulating all such kinds of Instruments) as that the Sound might enter the Ear without any Refraction, but as now they are generally made I refer them to _Refracted Audition_. 2. As to the _Medium_, I know not how that, by any contrivance of Art, can advantage _Direct Hearing_, otherwise than I have declar'd already in the propagation or conveyance of Sounds, though to the Refracting or Reflecting of them it may very much conduce; of which presently. And so I have done with the first part of my present undertaking, which is the _Comparison of Direct Vision and Audition_, as to their Improvements from Art. The rest follow. Wherefore, II. Concerning _Refracted Vision_ and its Comparison, I observe, That _Refracted Vision_ is always made _Ex parte Medii_, as _Reflected_ is _ex parte Objecti_. And therefore, though _Direct Vision_ may be help'd _ex parte Objecti, Medii vel Organi_, yet _Refracted_ can be improv'd only _ex parte Medii_, and _Reflected_ _ex parte Corporis oppositi_ alone. Unless it be in a mixt or compound Vision, that is _Refracto-Reflext_, when the reflext Rays pass to the Eye through a refracting Medium, such as the _Medium Internum_, contain'd in the Body of the Eye, always is. So that in truth, all Vision is _Refracted_ by an internal Refraction made in _ipso Oculo_. And all that I have spoken of _Vision_ holds true of _Hearing_ also, both _Refracted_ and _Reflext_, and therefore need not be repeated. _Refracted Vision_ arises from the different _Density_, _Figure_, and _Magnitude_ of the Medium, which is somewhat alter'd also by the diverse incidence of the visible Rays. And so it is in _Refracted Hearing_, all these Causes concur to its Production, and some others to be hereafter consider'd.