The figures in the above table apply in gene diameter of 1 or unity, that is 1 inch, 1 foot, 1 so forth, provided we remember that the 1 the chord is in the same unit as the diameter. ample, referring to the table to lay off 34 equal s a 1-foot circle, the dividers must be set to .0923 88. Volume and Area of Solid Rings.-Fi shows a solid ring with a circular cross secti length of the ring is the length of the dotted li cumference drawn through the center of the cro .0498 .0491 .0483 .0476 .0469 .0462 .0455 .0449 .0442 .0436 .0430 .0424 .0419 .0413 .0408 .0403 .0398 .0393 .0388 .0383 eral for a yard and length of For ex spaces on foot. gure 179 on. The Fine or cir the ring. The entire area or surface of ring equals the circumference of cross section of the ring times length of the dotted circle shown diameter "D"-that is Entire area of ring The volume of the ring equals area of cross section of the ring ti the length of the dotted circle sho of diameter "D,” that is, In general for a circular ring of an its entire area equals the product section times the circumference of th the center of gravity of its cross s gravity of the section is the point i it would balance if made of cardbo The volume of a ring of any shap the product of the area of its cross cumference of the circle drawn gravity of its cross section. 1. Find the area of the indicator c using the method explained in article 77 taken on the figure. (Read distances inch.) 2. Figure 181 shows the cross section E 60"Di FIG. 18 FIG. 180. 4. What length of arc is intercepted by a 29° central circle whose diameter is 2.8 in.? 5. If the minute hand on a tower clock is 61⁄2 ft. long what distance does its end move from 10:10 A. M. to 10:2 6. Find the area of cross section of a hollow cast-iron -24" Diam 10 FIG. 182. FIG. 183. dimensions shown in Fig. 182. If the column is 14 ft. its weight if cast iron weighs .26 lb. per cu. in. 7. Find the circumference and area of an ellipse wh and minor axes are respectively 12 in. and 7 in.. 8. Find the length of belt required to connect two 18whose centers are 8 ft. apart. Open belt. Piam 81. angle in a g, through :24 A. M.? column of 11. Find the length of belt required f belt is crossed. 12. What distance would you take centers on a 14-in. diam. circle? 13. Find the volume and area of Find its weight if made of in Fig. 183. long, find FIG. 184. 14. Find the area of a piece of sheet t in Fig. 184, by finding first the areas of r and adding to these the areas of triangl hose major OJ. Dition. - ation to the Engusi y measurement having as standards of length t foot, inch, and so forth, and for units of weight pound, and ounce, there is a system called the System having as a standard of length the meter w little longer than the yard. It contains 39.37 in same system has as a unit of weight the gram, whic part of a pound. 1 453.6 The meter is divided into one hundred equ called centimeters, or hundredths of a meter. these centimeters make 10100 or 10 meter called a Decimeter. For fine measurements of we centigram or 100 gram and the milligram o gram are used. For larger measurements of the kilogram or 1000 gram weight is used. The measurement of areas and volumes are terms of units of volume derived from the units o described above. The metric system is that used in science, that ics and chemistry, and in some countries is the used for common as well as scientific measuremen 90. The Metric Units.-The metric units are as |