36 Nature-Study Agriculture 



7. Plant seeds in two pots, the first one filled with earth from 

 the surface of the ground, and the other filled with earth taken 

 from a depth greater than the plow ever reaches. Explain the 

 results. 



8. Set out a vessel with straight sides and measure the first 

 rainfall. If there is snow, melt it before measuring. 



9. To find how much water different kinds of soil are able 

 to hold, proceed as follows : Wrap a string around several times 

 near the bottom of a large bottle. Wet the string with kerosene, 

 and after setting it on fire turn the bottle slowly till the fire goes 

 out. Then put the bottle into water, and, if necessary, tap it 

 with a hammer. It will break at the heated line, because of the 

 strain due to the sudden cooling and contraction. Tie cloth over 

 the mouth of the bottle and fill with dry sand. Fill several other 

 such bottles with clay, loam, silt, etc. (Fig. 19). Find how much 

 water each will hold without any draining through into a glass be- 

 low. (Tin cans with holes punched in the bottoms will do instead 

 of bottles.) 



10. Put several glass tubes of different bores in a cup of water. 

 Notice that the smaller the tube the higher the water is drawn by 

 capillary force (Fig. 21). 



V ii. Set a brick in shallow water and watch the capillary rise 

 of the water (Fig. 21). 



12. Lay two pieces of glass together (Fig. 21). Separate 

 them on one side by putting a match between them. Dip one 

 end of the glasses in water and observe that near the side 

 where they touch the water is drawn higher than on the other 

 side. 



13. Set two glasses side by -side, one full of water, the other 

 empty. Connect the two by a lamp wick (Fig. 21). 



14. Set a pan of water and a pan of sand in the hot sun or near 

 a stove. Which warms first ? 



