It may, perhaps, be remarked that undue prominence has been given to the tertiary and cretaceous formations, but it is urged in extenuation that they happen to underlie two of the most important cities in Europe, and that they have, in consequence, received a more thorough investigation than has been accorded to other districts. The records of wells in many formations are singularly scanty and unreliable, but it is hoped that the time is not far distant when the water-bearing characteristics of strata, such as the new red sandstone and permian, will receive proper attention, and that correct official records of well-work will be found in every locality, as this alone can rescue an important branch of hydraulic engineering from the charge of empiricism. In the course of the work the writings of G. R. Burnell, C.E., Baldwin Latham, C.E., M. Dru, Emerson Bainbridge, C.E., G. C. Greenwell, and other well known authorities, have been freely referred to, particular recourse having been had to the works of Professor Prestwich, F.G.S. I am indebted to Geo. G. André, C.E., F.G.S., Messrs. S. Baker and Son, and Messrs. T. Docwra and Son, for many suggestions and much valuable information; to Messrs. Docwra special thanks are due for some of the important sections illustrating chapter vii. Any claim to attention the book may deserve is based upon its being an attempt to embody, in a collected form, facts and information derived from practice, or from various sources not accessible to the majority of those engaged in the superintendence, or otherwise interested in the construction of wells. ERNEST SPON. 16, CRAVEN STREET, CHARING CROSS, _June, 1875_. SINKING AND BORING WELLS. CHAPTER I. GEOLOGICAL CONSIDERATIONS. Nearly every civil engineer is familiar with the fact that certain porous soils, such as sand or gravel, absorb water with rapidity, and that the ground composed of them soon dries up after showers. If a well be sunk in such soils, we often penetrate to considerable depths before we meet with water; but this is usually found on our approaching some lower part of the porous formation where it rests on an impervious bed; for here the water, unable to make its way downwards in a direct line, accumulates as in a reservoir, and is ready to ooze out into any opening which may be made, in the same manner as we see the salt water filtrate into and fill any hollow which we dig in the sands of the shore at low tide. A spring, then, is the lowest point or lip of an underground reservoir of water in the stratification. A well, therefore, sunk in such strata will most probably furnish, besides the volume of the spring, an additional supply of water.