Dalton's training in physical science--He revives and renders quantitative the atomic theory--The term "atom" is applied by him to elements and compounds alike--His rules for chemical synthesis 106 CHAPTER IV. ESTABLISHMENT OF GENERAL PRINCIPLES OF CHEMICAL SCIENCE (_continued_)--PERIOD OF DAVY AND BERZELIUS. Electro-chemistry--The dualistic theory developed by Berzelius--Davy's work on acids, alkalis, and salts--He proves chlorine to be an element--His discovery of the safety-lamp 155 CHAPTER V. THE WORK OF GRAHAM. Graham traces the movements of molecules--He distinguishes between colloids and cystalloids--Dialysis 232 CHAPTER VI. RISE AND PROGRESS OF ORGANIC CHEMISTRY--PERIOD OF LIEBIG AND DUMAS. The barrier between inorganic and organic chemistry begins to be broken down--Woehler prepares urea--Dumas opposes the dualistic system of Berzelius--Liebig's conception of compound radicles--His work in animal and agricultural chemistry 252 CHAPTER VII. MODERN CHEMISTRY. The relations between composition and properties of bodies are developed and rendered more definite--Physical methods are more largely made use of in chemistry--Spectroscopic analysis 294 CHAPTER VIII. SUMMARY AND CONCLUSION 316 HEROES OF SCIENCE. INTRODUCTORY. As we trace the development of any branch of natural knowledge we find that there has been a gradual progress from vague and fanciful to accurate and definite views of Nature. We find that as man's conceptions of natural phenomena become more accurate they also for a time become more limited, but that this limitation is necessary in order that facts may be correctly classified, and so there may be laid the basis for generalizations which, being definite, shall also be capable of expansion. At first Nature is strange; she is full of wonderful and fearful appearances. Man is overwhelmed by the sudden and apparently irregular outbreaks of storms, by the capricious freaks of thunder and lightning, by the awful and unannounced devastations of the volcano or the earthquake; he believes himself to be surrounded by an invisible array of beings more powerful than himself, but, like himself, changeable in their moods and easily provoked to anger. After a time he begins to find that it is possible to trace points of connection between some of the appearances which had so overpowered or perplexed him.