PREFACE. 



THE present number constitutes the third yearly volume of the 

 Annual of Scientific Discovery. The Editor, in its preparation, has 

 .selected from the great mass of yearly accumulative matter, such 

 subjects as to him seem most important and interesting. The 

 selection and arrangement of the articles have also been made with a 

 special view of illustrating the progress of natural and physical 

 science, in all their departments, from year to year, each volume 

 taking up the history and narration as dropped in the preceding one, 

 in such a way, that a complete series of the work shall present, as 

 nearly as possible, a complete scientific history, not only of each 

 year, but also of the whole time elapsed since the publication of the 

 first volume. 



That the Annual has imperfections, we would neither endeavor to 

 disguise nor conceal. The progress of invention and discovery, of 

 improvement and application, is so rapid, unceasing and continuous, 

 that it would require a volume many times the size of the present 

 to record, even in a summary manner, all that transpires of scien- 

 tific interest in the course of a single year. Some topics of impor- 

 tance, from their abstruse and technical character, have been 

 necessarily omitted. To a certain extent, also, the researches and 

 discoveries relating to organic chemistry and mineralogy have been 

 passed over ; the limits of the present work would not suffice for 

 their entire publication, and the interest attached to them, although 

 great, is almost entirely confined to those engaged exclusively in 

 scientific pursuits. If, also, in rejecting some subjects of impor- 

 tance, we have, in this age, when falsity and exaggeration in regard 

 to matters of invention and discovery are so common, inserted some 

 articles not wholly trustworthy, the Editor would plead, as an ex- 



