notice that his studies gave him pleasure. By degrees he became
able to solve his sums correctly in every form of arithmetic,
finally even getting as far as to extract two and three roots.

"We soon noticed that Rolf could also recognize letters and
numerals. He read his own name easily, for when anyone began to
write it on the typewriter he instantly started wagging his tail
with delight. Our greatest desire now was to devise some means of
communication with him and I therefore began with the following
simple explanation:

"'Rolf,' I said, 'if you could say yes and no, you would be able to
talk to us; now, look here! when you want to say _yes_, give us
your paw _twice_, and if _no_, then give it _three_ times,' and I
at once put this suggestion to an easy test, for I asked him if he
would like to be spanked--and he returned a decided _no_! Then I
asked him if he would like some cake, to which a prompt and joyful
affirmative was given. I saw therefore that Rolf understood me, and
upon this mutual basis I proceeded carefully to build. At length
his alphabet came into being--he having, with the exception of one
or two letters, put it together entirely by himself. It was
constructed thus: I would ask him, for instance, 'Rolf, how many
taps with your paw are you going to give me for _a_?' and he then
gave me a number which I carefully noted down. To my inexpressible
pleasure I found that Rolf never forgot the numbers he had given,
though I, to this day, must have my notes to hand whenever Rolf
wishes to tap out anything. It is also remarkable that on a nearer
investigation of his "alphabet" it becomes evident that the letters
Rolf requires least are made up of the highest numbers, whereas
those to which he has constant recourse have their equivalents
among the lower numbers. The letters q, v, x, Rolf never uses, as
though he wished to prove to me that they are entirely useless and
superfluous. Rolf can recognize any money that is shown him and
counts the flowers in a bunch according to their colours and
varieties. He can also differentiate the high and the deep tones on
any instrument, and he is even capable of telling the number of
tones struck in a chord. His memory is marvellous; he remembers
names and numbers over quite a period of time, once he has heard
them, and he is read