223. The accompanying table shows the production in thousand feet of the leading kinds of lumber for 3 yrs. What was the total production for each year? What was the per cent of increase or decrease of each kind from 1899 to 1906? What the total per cent of increase or decrease?

224. A tree weighing 10,000 lbs. when dry is 50 per

cent carbon.

How many pounds of carbon are there in

the tree?

225. Carbon dioxide being carbon, and all the carbon of the tree being derived from carbon dioxide, how many pounds of carbon dioxide are required to furnish the carbon in the tree of the last problem?

226. Air being .33% carbon dioxide, how many pounds of air are required to furnish this amount of carbon dioxide ?

227. Air weighing 31.074 grs. per 100 cu. ins., how many cubic yards of air are required to furnish the amount of carbon used in the growth of the tree mentioned above?

228. There are in the atmosphere of the earth about six billion pounds of carbon dioxide. How much carbon does it contain? For how many trees like that of problem 224 would this suffice?

229. An adult exhales daily into the air about 245 g. of carbon. Estimating the earth's population at 1400 million, how much carbon is thus restored daily to the air? 230. Wood, coal, etc., in burning restore their carbon to the air. One manufacturing works thus restores from

the coal burned about 5,100,000 lbs. of carbon.

231. A forest consisting of how many trees like the one mentioned in problem 224 could be raised from this carbon?

232. One square meter of pumpkin or sunflower leaf in a summer day of 15 hrs. makes 25 g. of starch which is

carbon. How many cubic meters of air are required to furnish the requisite carbon? How long a room 3 m. wide and 3 m. high would be required to contain it?

233. Convert all the measurements of the last problem into English measure, and solve.

per

234. If Alfalfa hay contains 10.44 per cent digestible protein, 39.6 per cent carbohydrates, and 1.2 per cent fats, and red-clover hay contains 6.8 per cent protein, 35.8 cent carbohydrates, and 1.7 per cent fats, what is the difference in the feeding value of a ton of Alfalfa and a ton of red clover, estimating digestible protein at 3 cts. a pound, carbohydrates at 1 ct. a pound, and fats at 21 cts. a pound?

235. On land worth $65 an acre Alfalfa is sowed and maintained for 4 yrs. at an expense of $30. The cost of harvesting the hay is $1.25 a ton; the crops are: 1st year 2.78 tons, 2d 3.15 tons, 3d 4.60 tons, 4th 4.28 tons. What is the profit on 9 acres, allowing 10 per cent interest on the value of the land, $12 a ton for hay, and $3 a ton for cost of baling and marketing?

APPENDIX

SURFACES OF SOLIDS

THE surface of a solid except its base or bases is called the Lateral Surface. The Entire Surface includes its bases. A solid, the base of which is a polygon and the sides of which are triangles meeting at a point or vertex, is called a Pyramid.

The distance from the vertex to the side of the base is called the Slant Height. If the sides and angles of the pyramid are respectively equal and the apex is

directly over the centre of the base, the pyramid is said to be regular.

The surface of a pyramid, as may be seen, is composed of a number of triangles with an altitude equal to the slant height of the pyramid and the bases forming the perimeter of the solid.

A solid, the base of which is a circle, and the surface of which tapers to a point or vertex, is called a Cone.

The lateral surface of a cone may be assumed to be made up of a number of infinitely small

triangles.

Hence, to find the lateral surface of a pyramid or cone, multiply the perimeter of the base by the slant height.

The portion remaining after a part of the top has been cut from a pyramid or cone is called a Frustum of a pyramid or of a cone.

The lateral surface of a frustum of a pyramid may be regarded as composed of a number of trapezoids, the sum of the parallel sides of which forms the perimeter of the

bases and the slant height of which equals the altitude of the frustum.

The lateral surface of a frustum of a cone may be considered as made of a number of infinitely narrow trapezoids.

To find the lateral surface of the frustum of a pyramid or of a cone, multiply half the sum of the perimeters of the two bases by the slant height.

A solid having equal polygons parallel to each other for its two ends and parallelograms for its sides is a Prism.

From the form of their bases, prisms are triangular, quadrangular, etc.

be

The lateral surface of a prism may regarded as a series of parallelograms, with their combined bases equal to the perimeter of the two bases of the prism and a height equal to the altitude of the prism.

To find the lateral surface of a prism, multiply the perimeter of the base by the altitude.

VOLUMES OF SOLIDS

The volume of a solid is the number of solid units it contains.

To find the volume of a prism, multiply the area of the base by the altitude.

A square prism has three times the solid contents of a pyramid. In like manner, the cylinder has three times the solid contents of the cone.

To find the volume of a pyramid or cone, multiply the area of the base by one-third the altitude.

The frustum of a pyramid or cone is equal to three pyramids or cones, the common altitude of which is the altitude of the frustum and the bases of which are the