societies established for the purposes of maintaining what they consider their rights-rights often of a very imaginary character, and ill calculated to advance their position or promote their individual interests. It is not my wish to enter here into the questions which these contests suggest. I am willing to forget bygone days and to look forward with sanguine hope to better times, when truer principles of freedom and social economy shall be acted upon, without destroying the independence and originality which have always been characteristic of an intelligent body of men for whom I entertain individually and collectively the highest veneration and respect. I have deemed it necessary to give this brief account of the habits and character of a body of men whose skill and spirit of perseverance has done so much for the advancement of applied science, and whose labours have still a large influence on the industrial progress of the country. I am, perhaps, better qualified for this task than most others, from having been associated with them from early life, so that an experience of some fifty years must be my excuse for having imposed this narrative upon the reader. For many years I have had it in contemplation to give an account of my own practical experience in millwright construction, but a multiplicity of engagements has combined with other causes to delay the work, and to modify considerably the original plan. This first volume, I hope, may contain reliable data and true principles for the successful guidance of the millwright in his professional duties. The present portion of the work treats of the first principles of mechanism generally, and proceeds to the discussion of the various constructions of prime movers. I hope shortly to complete the work by a treatise on the new system of transmissive machinery, and on the arrangements necessary for imparting motion to the various descriptions of mills. The accumulation, storage, and measurement of water has received attention; as well as the construction of prime movers depending upon this motive power, including the best forms of water-wheels, according to my own practice, and the more recently introduced varieties of turbines. In discussing the principles of the steam engine I have inserted a short treatise on the properties of steam, derived in part from researches carried on under my own superintendence, bearing on the density of saturated steam and the law of expansion of superheated steam. To this has been added a chapter on engines and boilers, their strength, powers, and principles of construction. It is evident that, in the present improved state of mill machinery, steam and water are the chief agents on which we depend for motive power. In former times the wind was also looked to as a source of power, but it is now very little employed, except in Holland and the fenny districts of this country, where it is still used for pumping and other operations where constant uniformity of action is not required. Notwithstanding the changes effected by steam, as windmills are not yet obsolete, I have given a short chapter on their mode of construction. In the prosecution of this work I have been ably assisted by my friend Mr. Thomas Tate, to whom I owe the chapter on the elementary principles of mechanism: as also to my assistant and secretary, Mr. William C. Unwin, to whose assiduous attention and love of science I am greatly indebted. |