The reader may set me down as a hopeless busybody， when Iconfess how much this man stimulated my curiosity， and how oftenI endeavoured to break through the reticence which he showed onall that concerned himself. Before pronouncing judgment， however，be it remembered how objectless was my life， and how little therewas to engage my attention. My health forbade me from venturingout unless the weather was exceptionally genial， and I had nofriends who would call upon me and break the monotony of mydaily existence. Under these circumstances， I eagerly hailed thelittle mystery which hung around my companion， and spent muchof my time in endeavouring to unravel it.
He was not studying medicine. He had himself， in reply to aquestion， confirmed Stamford’s opinion upon that point. Neitherdid he appear to have pursued any course of reading which mightfit him for a degree in science or any other recognized portalwhich would give him an entrance into the learned world. Yet hiszeal for certain studies was remarkable， and within eccentric limitshis knowledge was so extraordinarily ample and minute that hisobservations have fairly astounded me. Surely no man would workso hard or attain such precise information unless he had somedefinite end in view. Desultory readers are seldom remarkable forthe exactness of their learning. No man burdens his mind withsmall matters unless he has some very good reason for doing so.
His ignorance was as remarkable as his knowledge. Ofcontemporary literature， philosophy and politics he appearedto know next to nothing. Upon my quoting Thomas Carlyle， heinquired in the na.vest way who he might be and what he haddone. My surprise reached a climax， however， when I foundincidentally that he was ignorant of the Copernican Theoryand of the composition of the Solar System. That any civilizedhuman being in this nineteenth century should not be aware thatthe earth travelled round the sun appeared to me to be such anextraordinary fact that I could hardly realize it.
“You appear to be astonished，” he said， smiling at my expressionof surprise. “Now that I do know it I shall do my best to forget it.”
“To forget it！”
“You see，” he explained， “I consider that a man’s brain originallyis like a little empty attic， and you have to stock it with suchfurniture as you choose. A fool takes in all the lumber of every sortthat he comes across， so that the knowledge which might be usefulto him gets crowded out， or at best is jumbled up with a lot ofother things， so that he has a difficulty in laying his hands upon it.
Now the skilful workman is very careful indeed as to what he takesinto his brain-attic. He will have nothing but the tools which mayhelp him in doing his work， but of these he has a large assortment，and all in the most perfect order. It is a mistake to think that thatlittle room has elastic walls and can distend to any extent. Dependupon it there comes a time when for every addition of knowledgeyou forget something that you knew before. It is of the highestimportance， therefore， not to have useless facts elbowing out theuseful ones.”
“But the Solar System！” I protested.
“What the deuce is it to me？” he interrupted impatiently； “you saythat we go round the sun. If we went round the moon it would notmake a pennyworth of difference to me or to my work.”
I was on the point of asking him what that work might be， butsomething in his manner showed me that the question wouldbe an unwelcome one. I pondered over our short conversation，however， and endeavoured to draw my deductions from it. Hesaid that he would acquire no knowledge which did not bear uponhis object. Therefore all the knowledge which he possessed wassuch as would be useful to him. I enumerated in my own mindall the various points upon which he had shown me that he wasexceptionally wellinformed. I even took a pencil and jotted themdown. I could not help smiling at the document when I hadcompleted it. It ran in this way：
Sherlock Holmes—his limits
1. Knowledge of Literature.—Nil.
2. " " Philosophy.—Nil.
3. " " Astronomy.—Nil.
4. " " Politics.—Feeble.
5. " " Botany.—Variable.
Well up in belladonna， opium， and poisons generally.
Knows nothing of practical gardening.
6. Knowledge of Geology. —Practical， but limited.
Tells at a glance different soils from each other. After walkshas shown me splashes upon his trousers， and told me by theircolour and consistence in what part of London he had receivedthem.
7. Knowledge of Chemistry. —Profound.
8. " " Anatomy. —Accurate， but unsystematic.
9. " " Sensational Literature. —Immense. He appearsto know every detail of every horror perpetrated in the century.
10. Plays the violin well.
11. Is an expert singlestick player， boxer， and swordsman.
12. Has a good practical knowledge of British law.
When I had got so far in my list I threw it into the fire in despair.
“If I can only find what the fellow is driving at by reconciling allthese accomplishments， and discovering a calling which needs themall，” I said to myself， “I may as well give up the attempt at once.”
I see that I have alluded above to his powers upon the violin.
These were very remarkable， but as eccentric as all his otheraccomplishments. That he could play pieces， and difficult pieces，I knew well， because at my request he has played me some ofMendelssohn’s Lieder， and other favourites. When left to himself，however， he would seldom produce any music or attempt anyrecognized air. Leaning back in his armchair of an evening， hewould close his eyes and scrape carelessly at the fiddle which wasthrown across his knee. Sometimes the chords were sonorousand melancholy. Occasionally they were fantastic and cheerful.