28 ELEMENTARY GENERAL SCIENCE CHAP. 



means of u squared " paper of this kind, the area of any figure 

 can be found by drawing the figure upon the paper and count- 

 ing the number of squares embraced by the boundary lines. If 

 " squared " paper is not available, the area is still easily found 

 by dividing it up into square centimetres with a T-square and set 

 squares. 



EXPT. 35. Draw an oblong, such as CEFD (Fig. 17), upon 

 squared paper and find the number of squares it contains. 

 Draw a parallelogram CABD with a base equal to the base 

 of the oblong, and a height equal to that of the oblong. Count 

 the number of squares in the parallelogram (counting the por- 

 tions of squares as quarters, halves, and three-quarters). The 

 number will be the same as that found for the oblong. No 

 matter what parallelogram is drawn, the area will be found to 

 be the same as that of an oblong on the same base and having 

 the same height. 



EXPT. 36. Draw a parallelogram on paper or thin card and 

 then cut it in two from corner to corner. You have now 

 two triangles, and by laying one on the other you will find that 

 they fit and are equal. 



EXPT. 37. Draw any irregular figure upon squared paper 

 and count the number of squares embraced by it. If the size 

 of the squares is known, the area of the figure can be deter- 

 mined in this way. The area of any irregular figure can 

 evidently be determined by tracing the figure upon squared 

 paper and counting the number of squares included by the 

 outline, or by actually dividing it into square centimetres as 

 shown above. 



Measurement of Volume. When we come to measure 

 volumes we are dealing with three dimensional spaces ; and 

 just as a plane surface or area measuring one foot in each of 

 the directions, length and breadth, is called a square foot from 

 the name of the figure which it forms, so a solid which is ob- 

 tained by measuring a foot in three directions, at right angles, 

 length, breadth, and thickness, is called a cubic foot, from the 

 name cube given to the solid so formed. Similarly using the 

 metric system, we may speak of a cubic metre, or a cubic 

 decimetre. 



The amount of space enclosed by a solid figure is called its 

 volume. The volume of a solid is the space it occupies or its 

 size. The volume of a vessel is the amount of space it encloses. 



