Cardan begins with a definition of Subtilty. "By subtilty I mean a certain
faculty of the mind by which certain phenomena, discernible by the senses
and comprehensible by the intellect, may be understood, albeit with
difficulty." Subtilty, as he understood it, possesses a threefold
character: substance, accident, and manifestation. With regard to the
senses he admits but four to the first rank: touch, sight, smell, and
hearing; the claims of taste, he affirms, are open to contention. He then
passes on to discuss the properties of matter: fire, moisture, cold,
dryness, and vacuum. The last-named furnishes him with a text for a
discourse on a wonderful lamp which he invented by thinking out the
principle of the vacuum. This digression on the very threshold of the work
is a sample of what the reader may expect to encounter all through the
twenty-one books of the _De Subtilitate_ and the seventeen of the _De
Varietate_. Regardless of the claims of continuity, he jumps from
principle to practice without the slightest warning. Intermingled with
dissertations on abstract causes and the hidden forces of Nature are to be
found descriptions of taps and pumps and syphons, and of the water-screw
of Archimedes, the re-invention of which caused poor Galeazzo Rosso,
Fazio's blacksmith friend, to go mad for joy. There are diagrams of
furnaces, of machinery for raising sunken ships, and of the common
steelyard. Cardan finds no problem of the universe too recondite to essay,
and in like manner he sets down information as to the most trivial details
of every-day economy: how to kill mice, why dogs bay the moon, how to make
vinegar, why a donkey is stupid, why flint and steel produce fire, how to
make the hands white, how to tell good mushrooms from bad, and how to mark
household linen. He treats of the elements, Earth, Air, and Water,
excluding Fire, because it produces nothing material; of the heavens and
light: metals, stones, plants, and animals. Marvellous stories abound, and
the most whimsical theories are advanced to account for the working of
Nature. He tells how he once saw a man from Porto Maurizio, pallid, with
little hair on his face, and fat in person, who had in his breasts milk
enough to suckle a child. He was a soldier, and this strange property
caused him no slight inconvenience. Sages, he affirms, on account of their
studious lives, are little prone to sexual passion. With them the vital
power is carried from the heart to a