INTRODUCTION. 1 1 



pheres. A less circle is that which, being parallel to a greater, 

 cannot pass through the centre of the earth, nor divide it into two 

 equal parts. The greater circles are six in number, the less ox\\y four. 



Equator. ..The first great circle is the Equator, or Equinoctial; by- 

 navigators called the Line. The poles of this circle are the same 

 with those of the woritl. It passes through the east and west 

 points of the earth, and divides it into the northern and southern 

 hemispheres. It is divided into 360 degrees, the use of which will 

 soon appear. 



Horizon. ..This great circle is represented by a broad circular piece 

 of wood encompassing the globe, and dividing it into the upper and 

 lower hemispheres. Geographers distinguish the horizon into the 

 sensible and rational. The first is that which bounds the utmost 

 prospect of our sight, when we view the heavens around us, apfia- 

 rently touching the earth or sea. This circle determines the ris- 

 ing or setting of the sun and stars, in any particular place ; for 

 when they begin to appear above the eastern edge, we say they rise ; 

 and when they go beneath the western, we say they are set. It ap- 

 pears thafeach place has its own sensible horizon. The other ho- 

 rizon, called the rational, encompasses the globe exactly in the mid- 

 dle. Its poles (that is, two points in its axes, each ninety degrees 

 distant from its plane as those of all circles are) are called the Ze- 

 nith and Nadir; the former exactly above our heads, and the lat- 

 ter directly under our feet. The broad wooden circle which repre- 

 sents it on the globe, has several circles drawn upon it; of these 

 the innermost is that exhibiting the number of degrees of the twelve 

 signs of the zodiac, viz. thirty to each sign. Next to this are the 

 names of these signs together with the days of the month. Besides 

 these, there is a circle representing the thirty-two rhumbs, or points 

 of the mariners compass. 



Meridian. ...This circle is represented by the brass ring cm which 

 the globe hangs and turns. It is divided into 360 degrees, and cuts 

 the equator at right angles ; so that, counting from the equator 

 each way to the poles of the world, it contains four times ninety de- 

 grees, and divides the earth into the eastern and western hemis- 

 pheres. This circle is called the meridian, because, when the sun 

 comes to the south part of it, it is then meridies or mid-day and then 

 the sun has its greatest altitude for that day, which is therefore call- 

 ed its meridian altitude. Now, as the sun is never in its meridian 

 altitude at two places east or west of one another at the same time, 

 each of these places must have its own meridian. There are com- 

 monly marked on the globe twenty-four meridians, one through 

 every fifteen degrees of the equator. 



Zodiac... .The Zodiac is a broad circle, which cuts the equator 

 obliquely; in which the twelve signs above mentioned are repre- 

 sented. In the middle of this circle is supposed another, called the 

 Ecliptic, from which the sun never deviates in his annual course, 

 and i'i which he advances thirty degrees every month. The twelve 

 signs are, 



7. Libra =2= . September 



8. Scorpio itl . October 



9. Sagittarius f . November 



10. Capricornus >J . December 



11. Aquarius jjj* . January 



12. Pisces x • February 



1. 



Aries 



T 



March 



2. 



Taurus 



« 



April 



3. 



Gt-mini 



n 



May 



1. 



C&ncer 



25 



June 



'->. 



Leo 



SI 



July 



c ,. 



Virgo 



m 



August 



