( 3^57 ) 
fiadiDg Oppofition on every fide^ maketh a percuffion m 
every point of each imaginary circle of the Tube 5 and again^ 
that the percuffion made in every fuch Circle ^ beingjeunda* 
lated to the Center of each of them r maketh there a much 
ftronger percuffion than that which was made in any fingle 
point or part of fuch Circlejforafhiueh as it may be prefumed^ 
that all the percuffions, made in any of thofe Circles^ are uni- 
ted in their feveral Centers 5 and that the percuffion in the 
Center would again dilate it felf by a Spherical Undulation, 
but meeting with oppoficion in every point of the Tube, an 
entire Cone of imaginary rays of Sound are reverberated to 
fome Center 5 in like manner as the S^n- beams are reverbe- 
rated from a poHflit fuperficies of a parabolical Concave to its 
proper focus. . And that therefore, as the Tube enlarges it felf, 
and the Circles both of Reundulation and Reverberation be- 
come greater , there muft needs be imagined ( according to 
him) a greater number of Rcundulating Circle^ and Rever- 
berating Rays, to meet in each refpedJive Center and Focus ^ 
whereby the fame voice is greatly augmented. 8. As to the 
Deraonftrative part of this Tube ^ and the exacSt Figure and 
Dimenfionsof it, he propofech to Mathematical Philofophers 
this PrcDblem, t^i^. 
What is the J^ght- lined, Curvi lined^ or Mixt Figure ^ ami 
what are its exa& Dimenfions 5 and what the Sphere of its 
affivity^ that befi and mofi magnifies Human Voyce ? 
L<iflly^ He fubjoins the Ufes of this Inftrament ; as, i . That 
in a Storm J or in a Dark night, when two Ships dare not 
come fo near one another as to be heard by any ordinary 
voice, by this Tube they may very eafily fpeak together at 
half araileoramilesdiftancejormorejif need be , elpecially 
if alternately they take the advantage of the Wind : And if 
that be fo ftrong, that but one of the Ships can fpeak with the 
Wind, the other may anfwer by figns^ though direftly againft 
it. 2. In a Storm it is of good u(e in a fingle Ship^ for hear- 
ing one Man giving order to all in a Ship* 3» By it an Ad- 
miral may in a Calm give immediate Orders to his whole 
Fleets asalfoa Governour may convey his Orders from a 
Sea- 
