When two elements combine and form more than one compound, the masses of one element that react with a fixed mass of the other are in the ratio of small whole numbers.

We must reason in natural philosophy not from what we hope, or even expect, but from what we perceive.

The beginning of civilisation is the discovery of some useful arts, by which men acquire property, comforts, or luxuries. The necessity or desire of preserving them leads to laws and social institutions. The discovery of peculiar arts gives superiority to particular nations ... to subjugate other nations, who learn their arts, and ultimately adopt their manners;- so that in reality the origin as well as the progress and improvement of civil society is founded in mechanical and chemical inventions.

Fortunately science, like that nature to which it belongs, is neither limited by time nor by space. It belongs to the world, and is of no country and no age. The more we know, the more we feel our ignorance; the more we feel how much remains unknown.

The three states of the caterpillar, larva, and butterfly have, since the time of the Greek poets, been applied to typify the human being,--its terrestrial form, apparent death, and ultimate celestial destination.

The most important of my discoveries have been suggested to me by failures.

If I am allowed to give a metaphorical allusion to the future state of the blessed, I should imagine it by the orange-grove in that sheltered glen on which the sun is now beginning to shine, and of which the trees are at the same time, loaded with sweet golden fruit and balmy silver flowers. Such objects may well portray a state in which hope and fruition become one eternal feeling.