MifceUanea Curiofa. 317 



fcarce practicable other wife to ufe them, where 

 the agitation of the Sea continually changes the 

 Direction of the Mortar, and would render the 

 Shot very uncertain, were k not that they are 

 pkced about 45 Degrees Elevation, where fere- 

 ral Degrees above or under, make very little dif- 

 ference in the Effect. 



In the precedent Difcourfe, I confidered all 

 the Proportions relating to the Motion of Pro- 

 jectiles, and gave a Solution to this Problem y vi\» 

 To bit an ObjeH above or below the Horizontal Line 

 with the great eft Certainty and leafl Force. That 

 is, that the Horizontal diftance of the Object be- 

 ing put ase b, and the Perpendicular Heighth 

 rr. h y the Charge reguifite to (hike the Object 

 with the greateft Advantage, was that which 

 with an Elevation of 45° would caft the Shot on 



the Horizontal Line, to the diftance of 4 bb -4- hh % 



when the Object was above the Horizon ; or 

 if it were below it, the Charge mud be leffer, lb 

 as to reach on the Horizon, at 4^ Elevation, 



no greater a Diftance than 4 lb hh — h ; 



that is, in the one Cafe, the Sum of the Hppo- 

 thenufal Diftance of the Object from the Gun, 

 and the Perpendicular Heighth thereof above the 

 Gun ; and in the othei Cafe, when the Object 

 is below the Horizon, the difference of the fame 

 per 47. 1 EucL. And I then (hew'd how to find 

 the Elevation proper for the Gun lo charged, eft. 

 As the Horizontal Diftance of the Object, to rhe 

 Sum or Difference of the Hypothenufal Diftance 

 and Perpendicular Height : So Radius to the 

 Tangent of the Elevation fought. But I was not 

 at that time aware that the aforefaid Elevation 



Y n did 



