XU 
CONTENTS. 
PAGE 
PUMPS AND PIT-WORK. 
151. The pit-work an important element 
in the consideration of the Cornish engine . 110 
152. Historical notice of improvements in 
pit-work . . . . . . .111 
153. Change from bucket to plunger 
pumps—Watt, Murdock, Lean . .112 
154. Requisites for the system of pumps 113 
155. General views of pumps and pit-work. ib. 
156. Main rod . . . . . ib. 
157. Lower or lifting pump . . .114 
158. Objections to lifting pumps . .115 
159. Upper or plunger pumps—advantages 
of this plan . . . . . . ib. 
160. Principal work done by the descending 
stroke of the pumps . . . . .117 
161. Balance required for the pump rods— 
balance bobs . . . . . . ib. 
162. Hydrostatic counterbalance . .118 
163. Care taken to retain the drainage in 
the upper levels . . . . . ib. 
164. Process of lowering the pumps when 
deepening a mine . . . . .119 
165. Peculiar Cornish terms connected 
with the pit-work . . . . . ib. 
166. Inclined shafts and horizontal rods . 120 
167. Examples of arrangements of pit- 
work—Wheal Vor mine . . . . ib. 
168. Pembroke mine . . . .121 
169. Pump valves . . . .122 
170. Protection of the pit-work from the 
effect of impure water . . . .123 
171. Apparatus for lifting the pumps, &c. 124 
ACTION OF THE ENGINE. 
172. General reference to Plate IV.— 
method of distinction adopted in this de 
scription . . . . • • .124 
173. In-door and out-door strokes of the 
engine . . • • • • .125 
In-door Stroke. 
174. Mechanism of in-door stroke . .126 
175. Regulation of the expansion tappets 127 
176. Regulation of the in-door stroke . ib. 
Out-door Stroke. 
177. Mechanism of out-door stroke . 128 
178. Regulation of the out-door stroke— 
compression of steam at the end of this stroke 130 
Interval between the Out-door and In-door Strokes. 
179. Opening of the exhaustion valve . 131 
PAGE 
180. Opening of the steam valve . .132 
181. Pause between the strokes, favourable 
to a good condensation . . . . ib. 
GENERAL REMARKS. 
182. Principal differences between the Cor 
nish and Boulton and Watt single-acting 
engines . . . . . . .133 
183. Facility of regulating the engine to its 
work afforded by the use of high-pressure 
steam ....... ib. 
184. Strength of machines form a limit to 
the use of a great degree of expansion— 
breakages from shock at commencement of 
stroke . . . . . . .134 
185. Sims’s improved double - cylinder 
engine . . . . . . .135 
186. Hocking and Loam’s anti-concussion 
arrangement . . . . . .137 
187. Explanation of duty report . . ib. 
188. Manner of making up the report and 
calculating the duty . . . . .147 
189. Objections brought against the cor 
rectness of the Cornish reports . . .148 
190. Correctness of the reports proved . ib. 
191. Erection of Cornish engines out of 
the county—the Old Ford engine . .151 
192. Alleged causes of error in the Cornish 
reports (shortness of stroke, leakage, loss by 
valves, &c.) answered . . . .152 
193. Objection to coal account answered . 155 
194. Progressive improvement of the duty 
forms the best answer to the objections to the 
published reports . . . . .156 
195. Coals used in Cornwall—their eva 
porative power — mode of ascertaining the 
quantity consumed, &c. .... ib. 
196. Mr. Enys’s Table of Observations on 
ten engines at the Consolidated and United 
Mines ....... 157 
197. Expedition with which engineering 
work is executed in Cornwall . . .159 
198. Management of the engines — men 
employed, &c. . . . . . . ib. 
199. Relations which subsist between the 
mining proprietor, engineer, and manufacturer, 
in Cornwall . . . • • • ib. 
200. Advantages of this arrangement . 160 
201. List of Cornish engineers and manu 
facturers . . . . • • .161 
Appendix . . . • • .162