I have thrown the substance of my results into Aphorisms, as Bacon had done in his _Novum Organum_. This I have done, not in the way of delivering dogmatic assertions or oracular sentences; for the Aphorisms are all supported by reasoning, and were, in fact, written after the reasoning, and extracted from it. I have adopted this mode of gathering results into compact sentences, because it seems to convey lessons with additional clearness and emphasis. I have only to repeat what I have already said; that this task of adapting the _Novum Organum_ to the {xii} present state of Physical Science, and of constructing a _Newer Organ_ which may answer the purposes at which Bacon aimed, seems to belong to the present generation; and being here founded upon a survey of the past history and present condition of the Physical Sciences, will I hope, not be deemed presumptuous. TRINITY LODGE, 1 _November_, 1858. {{xiii}} TABLE OF CONTENTS. PAGE PREFACE **iii BOOK I. APHORISMS CONCERNING IDEAS. APHORISMS I.--XVIII. Ideas in general 5--7 XIX.--XLIV. Ideas in the Pure Sciences 8--12 XLV.--LV. Ideas in the Mechanical Sciences 13--15 LVI.--LXXI. Ideas in the Secondary Mechanical Sciences. 15--18 LXXII.--**LXXIII. Ideas in the Mechanico-chemical Sciences 18 LXXIV.--LXXIX. Ideas in Chemistry 18 LXXX.--LXXXI. Ideas in Morphology 19 **LXXXII.--C. Ideas in Classificatory Science 20--23 CI.--CVI. Ideas in Biology 23--24 CVII.--CXVII. Ideas in Palæontology 24--26 BOOK II. OF KNOWLEDGE. CHAP. I. OF TWO PRINCIPAL PROCESSES BY WHICH SCIENCE IS CONSTRUCTED 27