ployments. It is well known that, by obeying the laws of Nature, we learn how to employ them; and by studying the principles of science, and the action of the human mind in original research, we may reasonably expect to learn the essential conditions upon which success in scientific discovery depends.

Hitherto the nature and methods of original scientific inquiry have been insufficiently studied, and the success achieved in it has, therefore, been attributed too much to accident, to strong imagination, and exceptional natural ability; and too little to the less brilliant qualifications of steady thought, self-development, industry, and perseverance. No pretence, however, is made to impart by extraneous aid the faculties of imagination and invention, and the quick perception of difference and resemblance. But whilst great aptitude for scientific discovery must, like any other rare and peculiar ability, be born in the man, it is certain that it may, like those other natural abilities, be assisted by advice and developed by experience; and to supply such advice is one of the objects of this treatise.

It must be remembered that the simple or qualitative discovery of new truths usually precedes quantitative research, and such further research must be conducted according to logical as well as mathematical rules. Hence the suggestions and remarks of the following treatise will be almost wholly confined to the logical aspect of the subject.

The very magnitude of the subject makes it impossible to treat it thoroughly. A complete treatise would

have included-1. The history of the art of scientific discovery, including all the various discoveries, chronologically arranged.1 2. The various principles of science upon which the art is based.2 3. The practical rules and methods in general use. 4. The special details of the modes of research in particular sciences. But, in the first place, the history of the subject has already been given by very able writers; in the second, I have been obliged to limit myself to qualitative discovery, because the method of such discovery is the basis of all quantitative and further research; and, in the third, to include only discovery in the sciences of Physics and Chemistry, because those sciences afford the most simple examples of experimental investigation, and may be accepted as simple types of the more complex and concrete ones. The treatise, therefore, embraces but a small portion of a great subject; it consists simply of a series of chapters, all of them written more or less with the practical view of aiding students in pursuing original scientific inquiry. For the history and philosophy of the subject I must refer the reader to the several books already named; and for special technical details of working he must consult books on the several sciences.

1 Consult Baden Powell's Historical View of the Progress of the Sciences; Whewell's History of the Inductive Sciences; Draper's Intellectual Development of Europe; Thomson's Histories of Chemistry and of the Royal Society; Buckley's Short History of the Natural Sciences; &c.

2 Consult Whewell's Philosophy of the Inductive Sciences; Herschel's Discourse on Natural Philosophy; Jevons's Principles of Science ; Thomson's Laws of Thought; Bain On the Senses and the Intellect ; and the various works on logic and the different sciences.

The book is divided into five parts-the first containing a general view of the subject; the second, general conditions of scientific research; the third, personal preparation for research; the fourth, actual working in the art; and the fifth, various special methods of discovery, classified, and illustrated by numerous examples. I have endeavoured to make the book as interesting to nonscientific persons as the nature of the subject will admit. I have also inserted remarks and suggestions which will probably assist young investigators in disciplining their minds for the avoidance of error, although those remarks may not always bear directly upon the principal object of the book.

As there is no subject so fruitful of strife as the discussion of theological hypotheses, I have avoided as much as possible all reference to the bearings of original scientific inquiry upon religious opinions. There are, however, various truths which apply both to scientific and religious views, and these I have inserted as illustrations of statements in science. As, also, various scientific men who have asserted that the actions of the human mind are dependent upon law have had such assertions treated with disbelief and hostility, I have adduced some of the evidence already existing in proof of such statements.1 I have also shown that even the chief rules of morality are based upon the great fundamental principles of science, especially upon that of causation; and I hope that other thinkers will develop this great truth and show its correctness

1 See pp. 127-133.

2

2 See page 521.

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and importance. It is by the pursuit, discovery, and tice of truth that man is enabled to approach the Infinite Source of all Truth; and they who understand not and love not the great truths of Nature, so far understand not and love not the Great Source of those truths.

Although I am conscious that the task I have undertaken of sketching an outline of a second Novum Organon is very imperfectly performed, I hope that this essay may be not only of some value to students who wish to engage in original scientific research, but also of interest to actual scientific investigators and philosophic thinkers; and it would, I consider, help the progress of scientific discovery, if investigators in each of the sciences were to publish a classified and illustrated list of all the special methods of discovery employed in their respective subjects, such as I have in these pages crudely attempted for those of Physics and Chemistry. The sciences of mathematics, geometry, crystallography, mineralogy, geology, geography, meteorology, physical and mental physiology, &c., being all of them amenable to experimental observation, might be advantageously treated.

A great many historical statements are made in this book, and as it is extremely difficult, if not impossible, to ascertain accurately the exact date and circumstances of all of them, it is probable that, notwithstanding all the care I have taken, some may be incorrect; I therefore beg the especial indulgence of my readers on this point, and I shall feel deeply indebted for any corrections which may be suggested to me. Many remarks which do not appear to be immediately related to the subject in hand

are practically applied in subsequent chapters. Lastly, as a statement is usually more likely to be credited if it be supported by the authority of great or ancient names, I have in many instances preferred to insert the opinions of others in confirmation of my conclusions rather than state my own.

My best thanks are due to the Rev. Sir G. W. Cox, Bart., for examining the manuscript and correcting the proof-sheets, and to Professor JEVONS, LL.D., F.R.S., for correcting a portion of them. The corrections were copied by my assistant, H. W. Brown.