Catflaps go back at least to Isaac Newton, who cut a hole in his study

door so that Puss could come and go without disturbing the creation of the

calculus. When Puss had kittens, Newton cut a smaller hole next to it. We’ve

just installed one of those fancy ‘electronic’ ones. The cat wears a magnet

round its neck, trips the switch, comes in. Easy! At least, that’s the theory.

The cats, of course, know better. I’m coming to the conclusion that mathematicians

and catflaps don’t mix.

We have two cats: a greedy grey and white one named Stripes, which according

to family legend has swallowed a basketball, and a finicky brown one rejoicing

in the name of Ms Garfield, except that we drop the ‘Ms’. Stripes was once

half of a double act with her sibling Star, but Star went to the great catflap

in the sky many moons ago. At night, the two beasts reside in palatial splendour

– beds on the central-heating boiler – in what is inevitably now called

the Futility Room.

There’s been a plain, ordinary catflap in the Futility Room door for

years; the cats nudge it open as if walking on eggs and then hurl themselves

through it at Mach 1.5 in the vain hope that for once they’ll get right

through before the flap swings back to trap their tails. But when a new

tomcat in the neighbourhood began paying court to our neutered females,

marking its territory in time-honoured fashion, we had to find something

more selective. Hence the hi-tech electroflap.

The new catflap turns out to need a slightly larger hole than the old

one, making installation simplicity itself. Stripes insists on looking through

the hole while it is being enlarged, but inquisitiveness is a feline prerogative

and in any case eight lives are probably ample. Despite arctic breezes,

both cats approve of the new flapless catflap, and look distinctly disappointed

when the hi-tech electroflap with clear plastic see-through door blocks

it up again.


Installation of the magnets on Stripes and Garfield is less simple (first

catch your cat . . . ), but once we have collared the beasts, the chunky

black items tuck neatly under their chins. Before attaching them, we fill

in our address on the little labels provided, baffled. Is there a danger

of losing the cats? Of the cats losing their way now that their route home

has a different catflap? Has anyone informed the manufacturers that cats

can’t read?

Finally we locate a relevant sentence in the manufacturer’s helpful

eight-language leaflet (and also discover that we have purchased an elektromagnetische

Katzenklappe, or chatiere electromagnetique). The sentence is: ‘It is recommended

that you complete the identity card as even if your cat is unlikely to get

lost, he may decide to lose his collar!’. I decide not to show this to our

two female cats, who would probably take the manufacturer to the Advertising

Standards Authority for sexism, but in a burst of precognition I write to

ask the price of a set of spare magnets.

The central problem now emerges: to persuade the cats to use the new

flap. They enjoy peering through the clear plastic see-through door, either

from the inside looking out or the outside looking in, or indeed one of

each; but it certainly doesn’t cross their minds that they can go through

the thing. Five years of training vanish in an instant. Stripes gives me

withering looks: You dummy, if you can see through it, then it’s a window,

not a ruddy catflap, OK?

In vain we explain the theory to our cats. ‘It’s got a reed switch,

Stripes, and a solenoid with a battery attached. When you put your nose

against the flap, the magnet closes the reed, current flows through the

solenoid, and this little piece of plastic that stops the flap from swinging

retracts into the body of the door. Got that? Fine, let’s give it a whirl.’

Encouraged by glimpses of a bowl of food (Garfield’s, naturally) through

the clear plastic see-through door, Stripes inserts nose into reed-switch

activation zone; solenoid goes click!, and Stripes leaps back a foot. This

repeats indefinitely. The manufacturers are clearly electronic engineers

not fully versed in feline psychology.

We console ourselves with the thought that the cats will soon learn

that the click indicates that the flap is ready to open. We come down next

morning to find both cats inside the house: great, they’ve cracked it. Then

we discover the catflap’s electronic innards reclining on the Futility Room

floor. The manufacturers have failed to screw the solenoid in place, and

one of the cats – universally suspected to be Garfield – has shoved hard

enough against the flap to dislodge battery, solenoid, and the little piece

of plastic that stops the flap from swinging. This has converted the catflap

back into a low-tech tailtrapping device, which all cats – including the

new neighbours’ tomcat – have recognised as a good old catflap. I locate

two self-tapping screws and remedy this deficiency, while recalling nervously

that reed switches are made of glass. A test fortunately reveals no damage.

The cats now appear to have mastered the art of presenting their magnet

to the flap, and for several days all seems well. Then, in the night, we

hear Garfield making a total pig’s breakfast of getting in. We know it’s

Garfield because Garfield usually makes a total pig’s breakfast of everything.

Despite her track record I optimistically mutter, ‘She’ll soon learn’, and

go back to sleep. In the morning we are greeted by Garfield’s face squashed

flat against the clear plastic see-through door, with the rest of the cat

not far behind, looking like a fur concertina. The battery has run flat.

The manufacturer claimed ‘nine months’; this one’s lasted three weeks.

We buy a new battery and hope the old one was run down, despite a sneaking

recollection that it was brand new. Next day, Stripes comes in with her

magnet somewhere around her left ear. Inspection (first catch your cat

. . . ) reveals that one of the two plastic clips holding the magnet to

the collar has broken. We recall that Stripes was scratching her chin vigorously

the previous evening. We further recall that Stripes always scratches her

chin vigorously, and phone the manufacturers (a) to place an order for a

spare set of magnets, (b) to complain about the flimsy design of the clips.

The manufacturer replies that the clips are deliberately made flimsy

so that the magnet breaks off rather than leaving the cat hanging in a tree,

but admits that most purchasers don’t see it that way and that the clips

have now been redesigned to be chinscratch-proof. We complain vigorously

enough to get a free replacement for Stripes’s magnet, and order two sets

of spares. I wrap Stripes’s broken magnet in strong tape and replace it

on her collar, otherwise the poor beast can’t use the flap. I stifle visions

of Stripes suspended from the top of a tall tree – or, more plausibly, inextricably

pinned by the magnet to a refrigerator door.

Next evening, Garfield, who adores rituals and is constantly inventing

new ones, comes up with a real dandy. She is apparently asleep in the Futility

Room, when Stripes wanders in and sits by the catflap, looking out through

the clear plastic see-through door. Stripes is the type of cat for whom

net curtains were invented – dead nosey. Garfield wakes up, looks down at

the catflap, and starts howling.

Because it is dark outside, and the Futility Room light is on, Garfield

has seen Stripes’s reflection in the clear plastic see-through door, and

thinks it’s the new neighbours’ tomcat. Stripes, who knows full well that

there’s no tomcat outside and up to that moment has been perfectly happy

just being nosey, hears the growls and beats a hasty retreat. In Garfield’s

estimation this amply confirms her theory, giving cause for redoubled growls.

Both cats now stare anxiously at the clear plastic see-through door, with

their fur standing on end.

I reckon Newton had it easy.

Ian Stewart is a professor of mathematics at the University of Warwick,

and the author of Does God Play Dice? and Game, Set, & Math.