tHl 
are the fmeso? all doubled Arches j to thej?<^^^^ of their doubled 
Prop. VIL The Jkmdes of Proje^HoHs made with the 
fame Vtlocity^ at feveral EkvdMns^ as the ^erfed fines of 
th^ doubled Andes of Elevation : As c h to ^ is 
r)r 
—QS to^—^W, and UK:=RU=^ BF, th^ Altitude of the 
rr — - 
4 
Proj^ffim ^^-^Now by the; foregoing Lemma ~-^=to the 
V erf ed fine of the double J^^/^', and therefore it will be as Ka- 
dim^ to verfed fine of double the Angle FGB^ fo an %th of Pdra- 
meters to the height of the Pro]eBion VK; and lb thefe heights 
at>fev9ral£/^V^^^^^^'^ ar^; ^s. ^^X^^^^}^^^^ D. 
Coro/larv, 
' from hence it is pkin,that the greateft Aititudt of the per- 
pendicular P^ojeStion is a ^th of Parameter, or half the greateft 
Prop. VIIL The GF, or times of the flight of a Pro-- 
jecl caft with the fame degree of velocity at different Eleva- 
tions y are as the fines the Elevations'. 
that is as R-^^mi fo/;^^' df Elet^diiMy fo^ the ParMMit to the 
//^e* GF ; fo the lines G¥ are as the fmesof Elevation^ and the 
Times are proportional to -thofe L^W/ ; wherefore the 
T/^^j' are as the Sines Etevation 'i Ergo cenfiat frofofitfd. 
Prop. IX. Prablem. A Proje^ion being made as you pleale, 
having the Diftance and Altitude / or Defcent of an Object ^ 
through which the Project palTes, together with the Angle 
of Elevation of the line of DireUit)n'^ to find the Parameter and 
Velocity y that is (in Fig. 2. ) having the Angle FGB, GM, 
and MX. ' ■ ' 
SolHfiah, As Kadi^^ to Secant of FGB, fb GM the dijlance 
given 
