( 51 1 ) 
TheReafonof which Enlargement of the Elements of 
Latitude is, to counterbalance the Inlargemcnt of the 
Degrees of Longitude. For in this Proje&ion, the Me- 
ridians being all parallel, a Degree of Longitude at(fup- 
pofej 60 Deg. Lat. is become equal to a Degree in the 
Equator, whereas it really is (on the Globes Surface) but 
half as much, the Radius of the Parallel of 60 Deg (that 
is its Cofine) being but half the Radius of the Equator. 
Therefore to proportion the Degrees of Latitude to thole 
of Longitude, a Degree (or Elemental Particle,)’ in the 
Meridian, is to be as much greater than a Degree for like 
Panicle) in the Equator, as the Radius of the Equator is 
greater than the Radius of the Parallel of Latitude, viz. 
its Cofim. 
In Fig . 3 let the Radiys C D reprefent half of the Equa- 
tor, DM an Arc of the Meridian; MS its Sine, C E its 
Secant ; then is CS equal to its Cofine : and C S : CM : : 
C D{—C M)\ C E, that is, as Cofine : to Radius : : fo 
is Radius : to Secant. The Cofines being then, in this 
Proje&ion, fuppos’d all equal to Radius, or (which comes 
to the fame) the Parallels of Latitude being all made 
equal to the Equator, the Radius of the Globe, at every 
point of Latitude, (by the precedent Analogy)is fuppo- 
ied equal to the Secant of Latitude ; and confequently 
the Elements (Minutes, &c.) of the Meridian mult be 
proportional to their refpe&ive Secants. 
The Way Mr Wright takes for making his Table of 
Meridional Parts , is by a continual Addition of Natural 
Secants, beginning at i Minute, and £b proceeding to 
8.) Deg. Dr. Wallis (in Phil. Tranf No .176.) finds the 
Meridional Part belonging to any Latitude by this S e . 
ties, putting S for its Natural Sine, viz.S -S 3 -{- ~ S 5 
r'£ 7 -j- - S J &c. which gives the Merid. fart required^ 
How to find the fame Mechanically by means of aneafi- 
Jy-conflru&ed Curve Line, is what I fliall now fhew. 
I. 
