not happen because the two orbits cut or intersect each other, and the moon's orbfr 

 is inclined 5 degrees 8 minutes to the plane of the ecliptic. Those two places where 

 the intersection takes place are called the nodes ; and an eclipse can only take place 

 when the sun, earth, and moon, are in conjunction (or in a line; at the time when 

 the moon is in one of the nodes. 



ECLIPSE OF THE SUN. An eclipse of the sun is caused by the moon so coming 

 between the sun and the earth as to prevent the rays of the former from falling on 

 certain portions of the latter. This occurrence can only happen at the time of new 

 moon, and when she is at or near one of her nodes. 



There is a great difference between an eclipse of the sun and eclipses of the moon 

 The light which the moon' supplies is borrowed from the sun, and when she is 

 eclipsed it is because the earth intercepts the sun's rays, and she is in darkness ; but 

 when the sun is eclipsed, he is still shining in all his splendour ; so that what is 

 termed an eclipse of the sun, is in reality an eclipse of the earth, caused by the moon 

 passing over the sun's disk, and thereby preventing his rays of light falling on a por- 

 tion of the earth. The moon being smaller than the sun, casts a shadow which eucla 

 in a point ; and, therefore, solar eclipses can only be s^en by those who are withia 

 the shadow of the moon at the time the solar eclipse takes place. 



THE TIDES 



The tides are certain movements produced in the waters which in part surround 

 the earth, by the attraction of the sun and moon, particularly the latter, upon 

 them. 



The waters immediately beneath the moon being attracted by her, are elevated into 

 a swell, or wave of high water ; at the same time, the waters on the opposite side 

 of the globe are also raised into a similar swell, owing to the attraction of the moon 

 upon the solid mass of the earth, tending to draw it away from the waters on the 

 opposite side. Simultaneously, also, the waters between toe tide swells are corre- 

 spondingly depressed, that is, it is there low water. Now, as the moon is constantly 

 revolving round the earth, so the waters follow her attractive influence ; and thus 

 we have two tides daily, at intervals of about 12^ hours. 



Tides are distinguished into neap tides and spring tides ; the difference may be 

 thus explained : sometimes the sun and moon are acting in conjunction, at other 

 times in opposition. Thus, at the time of new moon and full moon, the sun and 

 moon are in conjunction, when their combined attraction causes the waters to be mere 

 elevated, and we have what are c died spring tides. Again, at the times of half-moon, 

 the sun and moon are in opposition, when we have but a slight elevation of the waters, 

 termed neap tides. 



THE FIXED STARS, 



Vast as the solar system we have been considering may appear, it is but a mere 

 point in the map of creation. When we pass from the planetary system to the 

 other regions of creation, we have to traverse in imagination a space so immense, 

 that it has hitherto baffled all the efforts of science to determine its extent. In these 

 remote and immeasureable spaces are placed those beautiful luminous bodies, the 

 Fixed Stars, each of which is equal or superior in magnitude and brilliancy to our 

 sun. The grandeur of the universe thus disclosed overwhelms the mind, and its 

 powers fail to comprehend the immensity of space, filled as it is with system after 

 system in apparently endless succession. 



The stars are divided into classes, according to their apparent magnitude, ranging 

 from the first to the sixteenth ; but all after the sixth magnitude are invisible to the 

 naked eye. The stars have, however, no appreciable magnitude at all, remaining 

 mere points of light under the greatest telescopic power. They vary simply in 

 brightness. To facilitate reference to the heavens, the stars havr been arranged into 

 groups, or constellations, of which there are 35 in the northerr hemisphere, and 46 

 in the southern. Ursa major is the most conspicuous and well known of the northern 

 constellations. Ursa minor is important from including the uorth polar star. Of 

 the southern constellations, Orion, with the groups in his vicinity, constitute the 

 richest part of the visible heavens ; Canis major, an the souih-east of Orion, con- 

 tains the beautiful star Sirius. The constellation of the Cross, not visible in our 

 latitude, is important to the mariner as indicating the direction of the south pole. 



Astronomers have endeavoured to ascertain the approximate distance of the fixed 

 stars. Professor Bessel made very carefuJ observations of a star in the constellation 

 of the Swan, and the result was, that although the earth is distant in July 190 mil- 

 lions of mil'es from the place it occupied in January, yet the difference in the angu- 

 lar bearing of the same star, observed at the two periods, was somewhat less tha;> 



