A thorough _education_ is indeed necessary to overcome this attitude; we must master and control our own wills, if we would bring ourselves into relation with the external world and appreciate its values. Without this preparation we cannot give due weight to the minute things from which science draws its conclusions. The capacity for sustained and accurate application to a task the object of which is apparently of very small importance, is indeed a most valuable asset to him who hopes to advance in science. Let us call to mind what a physicist does to place an instrument absolutely level; how patiently he turns first one screw and then another, tries again and again, slowly and carefully: and to what end? to procure an absolutely horizontal direction for a surface. When this measure of comparison is established in hard metal, how carefully it must be preserved to ensure that the oscillations of temperature shall not modify the length even in the most infinitesimal degree; for this would be fatal to the scientific use of the instrument in measuring horizontals. And yet how slight a thing in itself is involved! the preservation of a measure! When the great chemist wishes to find out whether _traces_ of a substance can give a reaction he seems to be playing with his phials like a little boy; he takes a retort and fills it with the substance he wishes to study, and then empties it; afterwards he fills it with water, and watches for the reaction; the reaction takes place; then again he empties the retort, fills it anew with water, and sees whether there is a further reaction. Thus he establishes the degree of dilution in which the substance will leave traces. In this case the minimum is the important thing; it was to find this imperceptible, negligible minimum that the great man acted like a child.