ii PREFACE. 



These difficulties are fairly grappled with, and, it is hoped, successfully mastered, 

 in the following Work. It includes every branch of Science ; from the study of matter 

 and forces, to the widest applications of scientific research for social purposes. To 

 the educated person, it offers a comprehensive resuini of all that is known in Ex- 

 perimental, Chemical, Mathematical, Mechanical, and Natural Science. To the 

 artisan, it affords a complete guide to each branch of Science, rising, by plain and easy 

 steps, from the very elements to the higher branches of each department. He will 

 equally find that, if his calling in life depend on the applications of Science, his wants 

 will be fully satisfied. The home student may undertake its perusal, with the 

 certainty of acquiring, without the aid of tutors, a general knowledge of each 

 branch of philosophy. In the arrangement of each subject, the circumstances of both 

 artisan and student have been specially borne in mind ; and it is hoped that no 

 person of ordinary intelligence, will find any difficulty in mastering any portion of 

 the Work. 



With respect to the authors of each section, it will be only requisite to remark, 

 that they stand at the head of their several departments. Without an exception, they 

 all occupy eminent positions in the world of Science, and have distinguished them- 

 selves as much by the diffusion as by the possession of scientific information. 



It will be unnecessary for us here to give any detailed explanation of the plan of 

 the Work. This will be found in the Introduction to Physics, which follows Lord 

 Brougham's admirable Discourse of the Objects, Pleasures, and Advantages of 

 Science. The arrangement of the subjects has been adopted with the view of 

 affording a thorough, but graduating course of study, so that, as the reader 

 progresses, he may be prepared to advance, by aid of that which he has already 

 learned. Generally speaking, it has been assumed that the reader knows nothing 

 of the subjects treated on; and this assumption will be highly appreciated by those 

 who have to pursue Science under any class of difficulties. 



In constructing an edifice, each stone adds both to its strength and height ; but 

 unless they be joined together by a suitable cement, the building will not itself be 

 strong. So, in a work of tliis kind, unless each subject be braced with the rest, each 

 may be individually complete, without rendering the work itself so. Tliis duty the 

 Editor has endeavoured to perform, by adopting the plan in which the Work is 

 ai -ranged, by notes of reference, explanatory remarks, &c. ; and even, in some cases, 

 by modifying the valuable contributions which he has had placed at his disposal. He 

 feels assured that their authors, animated with him in a desire to spread knowledge, 

 will readily pardon the liberty he has so taken, if their readers are in any way 

 benefited by such a course. In Nature, we observe that the beauty of the landscape 

 consists in the harmony of its outlines ; so in Science, whose only object is to unfold 

 the hidden laws of nature, a similar harmony of construction must exist, if we would 

 successfully impress its students with a sense of its beauties and perfections. Its 

 divisions must bo numerous, owing to the imperfections of human intellect. ; yet all 

 have ouo origin, tend to one end, and are in unison iu their great design. 



J. W. 



