ut the clay down upon the slab, drew a pruning-knife
from his pocket, cut two branches from an elder tree, and began to
clean them of pith by blowing through them, as if Raphael had not been
present.

"There are the rudiments of the apparatus," he said. Then he connected
one of the wooden pipes with the bottom of the flower-pot by way of
a clay joint, in such a way that the mouth of the elder stem was just
under the hole of the flower-pot; you might have compared it to a big
tobacco-pipe. He spread a bed of clay over the surface of the slab, in a
shovel-shaped mass, set down the flower-pot at the wider end of it, and
laid the pipe of the elder stem along the portion which represented the
handle of the shovel. Next he put a lump of clay at the end of the elder
stem and therein planted the other pipe, in an upright position, forming
a second elbow which connected it with the first horizontal pipe in such
a manner that the air, or any given fluid in circulation, could flow
through this improvised piece of mechanism from the mouth of the
vertical tube, along the intermediate passages, and so into the large
empty flower-pot.

"This apparatus, sir," he said to Raphael, with all the gravity of an
academician pronouncing his initiatory discourse, "is one of the great
Pascal's grandest claims upon our admiration."

"I don't understand."

The man of science smiled. He went up to a fruit-tree and took down a
little phial in which the druggist had sent him some liquid for catching
ants; he broke off the bottom and made a funnel of the top, carefully
fitting it to the mouth of the vertical hollowed stem that he had set in
the clay, and at the opposite end to the great reservoir, represented
by the flower-pot. Next, by means of a watering-pot, he poured in
sufficient water to rise to the same level in the large vessel and in
the tiny circular funnel at the end of the elder stem.

Raphael was thinking of his piece of skin.

"Water is considered to-day, sir, to be an incompressible body," said
the mechanician; "never lose sight of that fundamental principle; still
it can be compressed, though only so very slightly that we should regard
its faculty for contracting as a zero. You see the amount of surface
presented by the water at the brim of the flower-pot?"

"Yes, sir."

"Very good; now suppose that that surface is a thousand times larger
than the orifice of the elder stem through which I poured the liquid.
Here, I am taking