SCIENCE OF COMMON THINGS. 97 



Origin of shooting stars. Zodiacal light. 



them ; their altitude is supposed to vary from six to 

 four hundred and sixty miles, the greatest number 

 appearing at a height of about seventy mites. 



636 What is their supposed velocity ? 



It is supposed to range from sixty to fifteen hundred 

 miles per minute. 



637* Are meteors and shooting stars at all times equally abundant f 



They are not some may be seen every clear night, 

 but they appear to return at certain periodical epochs, 

 when they descend literally in showers. 



638 What are the periods when they may be noticed most abundantly f 



On the 9tk and Wth of August, and the 12^A and 

 13t/t of November. 



They have also been noticed in unusual abundance on the 18th of Octo- 

 ber, the- 6th and 7th of December, the 2d of January, the 23d and 24th of 

 April, and from the 18th to the 20th of June. 



639 Do the shooting stars appear to emanate from any particular part 

 of the heavens ? 



The majority seem to start from a point in the con- 

 stellation Perseus, and undoubtedly far beyond the 

 limits of our atmosphere. 



63O What is the zodiacal light f 



It is a singular luminous appearance seen in the 

 horizon before sunrise and after sunset, most conspicu- 

 ously in the months of April and May. 



Observations made during the year 1855 seem to conclusively prove 

 that the appearance known as the " zodiacal light " is occasioned by a 

 ring of nebulous matter encircling and pertaining to the earth. 



CHAPTER YII. 



THE PUMP AND BAROMETER. 



631 Why, when we suck up a liquid with a tube or straiv, does th& 

 liquid rise to the mouth 1 



One end of the tube being placed between the lips, 



