174 LABORATORY LESSONS IN GENERAL SCIENCE 



that an eclipse of the sun is total rather than partial ? What 

 change in the moon's distance from the earth when it is 

 directly in line between an observer and the sun will result 

 in its not wholly covering the sun's disk? The moon will 

 then appear as a dark body, and the sun as a ring of light 

 all round the moon's edge an annular (ringlike) eclipse. 

 Make a diagram showing these conditions. 



FIG. 76. Diagram showing conditions for solar and lunar eclipses. 



6. Total solar eclipses are very rare occurrences for any 

 one locality on earth. What evident connection is there 

 between this infrequency and (a) the length of the moon's 

 shadow ; (6) the size (cross section) of the umbra near its 

 apex? 



7. From the diagram above find the apparent reason 

 why the moon gets into the earth's shadow (lunar eclipse) 

 more often than an observer on the earth is in the moon's 

 shadow (solar eclipse). 



8. The period of the earth's revolution about the sun is 

 somewhat more than 365 days, while that of the moon about 

 the earth is 28 days. How many full moons per year are 

 possible? How many total eclipses of the moon? As- 

 certain from the almanac (or otherwise) how many are to 

 occur during this calendar year? Why are there no more? 



9. Make a drawing that shows the sun, the earth and its 

 moon, and Jupiter with at least one of its moons, so arranged 

 as to represent : 



