a simple clepsydra; then there are added marks indicating the
subdivisions of time, then a water gauge causes a hand to move around a
dial, then two hands for the hours and minutes; then comes a great
moment--by the use of weights the clepsydra becomes a clock, at first
massive and cumbersome, later lightened, becoming capable, with
Tycho-Brahe, of marking seconds; and then another moment--Huyghens
invents the spiral spring to replace the weights, and the clock,
simplified and lightened, becomes the watch.

_2. Special Characters_

The special characteristics of the mechanical imagination being the
marks belonging to this type, we shall study them at greater length.

(I) There is first of all, at least in great inventors, an inborn
quality,--that is, a natural disposition,--that does not originate in
experience and owes the latter only its development. This quality is a
bent in a practical, useful direction; a tendency to act, not in the
realm of dreams or human feeling, not on individuals or social groups,
not toward the attainment of theoretical knowledge of nature, but to
become master over natural forces, to transform them and adapt them
toward an end.

Every mechanical invention arises from a need: from the strict necessity
for individual preservation in the case of primitive man who wages war
against the powers of nature; from the desire for well-being and the
necessity for luxury in growing civilization; from the need of creating
little engines, imitating instruments and machines, in the child. In a
word, _every particular invention, great or small, arises from a
particular need_; for, we repeat again, there is no creative instinct in
general. A man distinguished for various inventions along practical
lines, writes: "As far as my memory allows, I can state that in my case
conception always results from a material or mental need.[124] It
springs up suddenly. Thus, in 1887, a speech of Bismarck made me so
angry that I immediately thought of arming my country with a repeating
rifle. I had already made various applications to the ministry of war,
when I learned that the Lebel system had just been adopted. My
patriotism was fully satisfied, but I still have the design of the gun
that I invented." This communication mentions two or three other
inventions that arose under analogous circumstances, but have had a
chance of being adopted.

Among the requisite qualities I mention the natural and necessary
preeminenc