was due to my ignorance of mathematics. Had I
understood the real meaning of what he asked, I should have been utterly
despondent.

Perhaps this problem of sixty miles a minute was not so impossible after
all. At any rate I could attempt, though I might not succeed. And
Rivarol came to my mind. I would ask him. I would enlist his knowledge
to accompany my own devoted perseverance. I sought his lodgings at once.

The man of science lived in the fourth story, back. I had never been in
his room before. When I entered, he was in the act of filling a beer mug
from a carboy labelled _Aqua fortis_.

"Seat you," he said. "No, not in that chair. That is my Petty Cash
Adjuster." But he was a second too late. I had carelessly thrown myself
into a chair of seductive appearance. To my utter amazement it reached
out two skeleton arms and clutched me with a grasp against which I
struggled in vain. Then a skull stretched itself over my shoulder and
grinned with ghastly familiarity close to my face.

Rivarol came to my aid with many apologies. He touched a spring
somewhere and the Petty Cash Adjuster relaxed its horrid hold. I placed
myself gingerly in a plain cane-bottomed rocking-chair, which Rivarol
assured me was a safe location.

"That seat," he said, "is an arrangement upon which I much felicitate
myself. I made it at Heidelberg. It has saved me a vast deal of small
annoyance. I consign to its embraces the friends who bore, and the
visitors who exasperate, me. But it is never so useful as when
terrifying some tradesman with an insignificant account. Hence the pet
name which I have facetiously given it. They are invariably too glad to
purchase release at the price of a bill receipted. Do you well apprehend
the idea?"

While the Alsatian diluted his glass of _Aqua fortis_, shook into it an
infusion of bitters, and tossed off the bumper with apparent relish, I
had time to look around the strange apartment.

The four corners of the room were occupied respectively by a
turning-lathe, a Rhumkorff Coil, a small steam-engine and an orrery in
stately motion. Tables, shelves, chairs and floor supported an odd
aggregation of tools, retorts, chemicals, gas-receivers, philosophical
instruments, boots, flasks, paper-collar boxes, books diminutive and
books of preposterous size. There were plaster busts of Aristotle,
Archimedes, and Comte, while a great drowsy owl was blinking away,
perched on the benign brow of Martin Farquhar Tupper. "