CHAPTER XVII. 183. Gravity Supplies 234 184. Masonry Conduits 234 185. Metal Conduits 236 186. General Formula for Discharge of Conduits—Chezy’s Formula 237 187. Kutter’s Formula 239 188. Hydraulic Gradient 241 189. Flow of Water in Large Masonry Conduits 244 190. Flow of Water through Large Closed Pipes 245 191. Change of Hydraulic Gradient by Changing Diameter of Pip 250 192. Control of Flow by Gates at Upper End of Pipe-line 251 193. Flow in Old and New Cast-iron Pipes—Tubercles 251 194. Timber-stave Pipes 253 CHAPTER XVIII. 195. Pumping and Pumps 254 196. Resistances of Pumps and Main—Dynamic Head 258 197. Duty of Pumping-engines 260 198. Data to be Observed in Pumping-engine Tests 261 199. Basis of Computations for Duty 262 200. Heat-units and Ash in 100 Pounds of Coal, and Amount of Work Equivalent to a Heat-unit 262 201. Three Methods of Estimating Duty 265 202. Trial Test and Duty of Allis Pumping-engine 265 203. Conditions Affecting Duty of Pumping-engines 266 204. Speeds and Duties of Modern Pumping-engines 266 CHAPTER XIX. 205. Distributing-reservoirs and their Capacities 267 206. System of Distributing Mains and Pipes 268 207. Diameters of and Velocities in Distributing Mains and Pipes 269 208. Required Pressures in Mains and Pipes 270 209. Fire-hydrants 270 210. Elements of Distributing Systems 270