15. Wash the remaining portion of the soil in Question 14 clean from all matter which does not settle promptly. Are there any pebbles left? If so, how large are they, and of what kind of stone? 16. Take a fresh sample of the soil. Mix it with distilled water in a flask. Boil the mixture. Allow it to settle. Filter. Divide the filtrate into two portions. Evaporate both, the larger portion in an evaporating basin over wire gauze, the smaller portion in a watch glass heated by steam. Is any residue left after heating to dryness? 17. Take a fresh sample of soil. Spread it on a clean sand bath and heat strongly with a Bunsen flame. Does any portion of the soil burn? Is there any change in its appearance after heating? 18. To a fresh sample of soil add some hydrochloric acid. Is there any effervescence? If so, what conclusions do you draw? 19. Make a solution of soil in distilled water, and filter as before. Is this solution acid, alkaline or neutral? Are you quite certain of your result? Did you test the distilled water with litmus paper? And are you sure that your litmus does not contain excess of free acid or free alkali? Peat. 20. Examine different varieties of peat collected (see Question 2) and describe the appearance of each. 21. Burn a fragment of each kind of peat on wire gauze. What do you notice? 22. Boil some peat with distilled water and filter the solution. What colour is it? Can you tell whether it is acid, neutral or alkaline? Evaporate some of the solution to dryness. Out-of-doors. 23. Describe the appearance of the soil in the flower beds (_a_) during hard frost, (_b_) in the thaw which follows a hard frost, (_c_) after an April shower, (_d_) in drought at the end of summer, (_e_) in damp October weather when the leaves are beginning to fall. 24. Is the soil equally friable at different times of the year? {131} 25. In what way do dead leaves get carried into the soil? 26. Can you find the worm holes in a garden lawn? in a garden path? 27. Take a flower bed or grass plot of small but known area (say 3 yards by 2 yards) and a watering can of known capacity (say 3 gallons). Find how much water must be added to the soil before some of the water will remain on the surface. What has been the capacity of the soil in gallons per square yard? 28. Take two thermometers. Lay one on the soil, the other with its bulb 3 inches deep in the soil. Compare their temperatures at morning, noon and night. 29. Find from the 25-inch Ordnance map the reference numbers of the fields near your school. Make a list of the fields, showing for what crop or purpose each field is being used. {132} INDEX Acid waters, 40 Air in soil, 16, 70, 95 Bars in estuaries, 122 Black soils, 36 Blowing sands, 22 Bricks, 10, 16-18 Chalk, 26, 96 Chalk soils, 110-112 Clay, 6, 9-21 Clay soils, 75, 100-102 Cliffs, 116-119