278 FERGUSON'S LECTURES. 



LECT. 



VIII. & IX. 



LECTURES VIII. AND IX. 



THE DESCRIPTION AND USE OF THE GLOBES, AND 

 ARMILLARY SPHERE. 



The ter- IF a map of the world be accurately delineated on a 

 spherical ball, the surface thereof will represent the 

 surface of the earth : for the highest hills are so incon- 

 siderable with respect to the bulk of the earth, that they 

 take off no more from its roundness, than grains of sand 

 do from the roundness of a common globe ; for the di- 

 ameter of the earth is 8000 miles in round numbers, 

 and no known hill upon it is three miles in perpendicu- 

 lar height. 71 



Proof of That the earth is spherical, or round like a globe, 



the earth's appears, 1. From its casting a round shadow upon the 



globular, moon, whatever side be turned towards her when she is 



eclipsed. 2. From its having been sailed round by 



several persons. 3. From our seeing the farther, the 



higher we stand. 4. From our seeing the masts of a 



ship, whilst the hull is hid by the convexity of the 



water. 79 



And that The attractive power of the earth draws all terres- 



it may be t r j a l b 0( ji es towards its center : as is evident from the 



peopled on 



all sides descent of bodies in lines perpendicular to the earth's 



any one surface, at the places whereon they fall ; even when 

 being in they are thrown off from the earth on opposite sides, 



danger of 



falling a p -d consequently, in opposite directions. So that the 



away from 



it. 



Note 71. The principal mountains of the earth have lately been 

 delineated on a terrestrial globe, contrived by an Italian. It will, 

 however, be apparent, from what our Author has stated above, that 

 the proportions could not have been accurately represented. 



Note 72. It may be proper to repeat what has been already stated, 

 that the earth is not a perfect sphere, but an oblate spheroio : the 

 poles being depressed, while the equator is expanded. 



