35 



18. \\'hy is snow a bad conductor of heat ? 



19. Pack snow in a quart cup until it is full and then let it melt, and 

 tell how full the cup is of water. What do you infer from this? 



2Q. Have you ever observed the grass to be green beneath snow 

 drifts ? 



21. Does snow evaporate as well as melt? 



22. How does the snow benefit the farmer and the fruit-grower ? 



23. Do the snow storms in your locality come from one general 

 direction all winter? (Cornell Home Nature-Study Leaflet). 



LXI. A Thunder Storm. 



The pupils should have access to a thermometer and a barometer, 

 and should learn to read and to interpret the readings. 



1. ^Miat is the state of the air before a thunderstorm? 



2. How could you tell there was a great deal of water-vapor in the 

 air at such a time ? 



3. Is the air near the ground colder or warmer than the upper air ? 

 How can you tell ? 



4. Are there currents of air ? In what direction ? Why ? 



0. Why should great banks of cumulus clouds appear ? 



6. Observe carefully the growth of this bank of clouds. Why is its 

 base flat ? 



T. Why does rain fall ? What is the function of the " dust " par- 

 ticles ? 



8. Why do hailstones often fall in a thunder storm? 



9. Account if you can for the lightning and thunder. At what time 

 of the day do thunder storms usually occur ? 



10. Describe the ^^assing away of the storm. 



LXII. The Work of Rain. 



Visit (1) a loose or sandy bank, and (2) a level field, after a rain 

 storm, and study the work of the rain. 



1. Ascertain where the deep furrows are made. 



2. What becomes of the constituents of the bank and field when car- 

 ried away ? 



3. What kinds of material are carried farthest by the water ? 



4. Examine a rain-pool, and, after it has dried, account for the posi- 

 tion of the deposits. 



5. Find a delta; studv its structure in detail. 



