Mifttllanea Curtofa. 257 



or lefs forceable, according to the Sinus of the 

 Angle of Incidence, or to the Perpendicular let 

 fall on the Plain, whence the vertical Ray (be* 

 ing that of the greateft Heat,) being put Radius^ 

 the force of the Sun on the Horizontal Surface 

 of the Earth wilHie to that, as the Sinus of the 

 Sun's Altitude at any other time. This being 

 allov/M for true, it will then follow, that the 

 time of the continuance of the Sun's Alining be- 

 ing taken for a Bafes, and the Sines of the Sun's 

 Altitudes erefted thereon as Perpendiculars, and 

 a Curve drawn through the Extremities of thofe 

 Perpendiculars, the Area comprehended fhall 

 be proportionate to the Collection of the Heat 

 of all the Beams of the Sun in that /pace of 

 time. Hence it will follow, that under the 

 Po'e the Collection of all the Heat of a tropi- 

 cal Day, is proportionate to a Rectangle of 

 the Sine of gr. into 24 Hours, or the Cir* 

 cumferenceof a Circle ; that is, the Sine of 23^ 

 gr. being nearly 4 Tenths of Radius ; as ts into 

 1 x Hours. On the Polar Heat is equal to that 

 of the Sun containing 12 Hours above the 

 Horizon, at 53 gr. height, than which the Sun 

 is not 5 Hours more elevated under the iEqui- 

 noctJal. 



But that this Matter may the better be un- 

 derstood, I have exemplified it by a Scheme, 

 (Tab. 4. Fig. %.) wherein the Area Z^G HH 9 is 

 equal to the Area of all the Sines of the Sun's 

 Altitude under the ^Equinoctial, eredted on the 

 refpe&ive Hours from Sun-rife to the Zenith j 

 and the Area © H H is in the fame propor- 

 tion to the Heat of the fame 6 Hours under 

 the Pole on the Topical Day; and OHHQ^ 

 is proportional to the collected Heat of 12 



S Hours, 



