An accident pointed out to Mad. de Rosier another resource in Matilda's education. One day Herbert called his sister Matilda to look at an ant, which was trying to crawl up a stick; he seemed scarcely able to carry his large white load in his little forceps, and he frequently fell back, when he had just reached the top of the stick. Mad. de Rosier, who knew how much of the art of instruction depends upon seizing the proper moments to introduce new ideas, asked Herbert whether he had ever heard of the poor snail, who, like this ant, slipped back continually, as he was endeavouring to climb a wall twenty feet high. "I never heard of that snail; pray tell me the story," cried Herbert. "It is not a story--it is a question in arithmetic," replied Mad. de Rosier. "This snail was to crawl up a wall twenty feet high; he crawled up five feet every day, and slipped back again four feet every night: in how many days did he reach the top of the wall?" "I love questions in arithmetic," exclaimed Matilda, "when they are not too difficult!" and immediately she whispered to Mad. de Rosier the answer to this easy question. Her exclamation was not lost;--Mad. de Rosier determined to cultivate her talents for arithmetic. Without fatiguing Matilda's attention by long exercises in the common rules, she gave her questions which obliged her to _think_, and which excited her to reason and to invent; she gradually explained to her pupil the relations of numbers, and gave her rather more clear ideas of the nature and use of the common rules of arithmetic than she had acquired from her writing-master, who had taught them only in a technical manner. Matilda's confidence in herself was thus increased. When she had answered a difficult question, she could not doubt that she had succeeded; this was not a matter that admitted of the uncertainty which alarms timid tempers. Mad. de Rosier began by asking her young arithmetician questions only when they were by themselves--but by and by she appealed to her before the rest of the family. Matilda coloured at first, and looked as if she knew nothing of the business; but a distinct answer was given at last, and Isabella's opinions of her sister's abilities rose with amazing rapidity, when she heard that Matilda understood decimal fractions. "Now, my dear Matilda," said Mad. de Rosier, "since you understand what even Isabella thinks difficult, you will, I hope, have sufficient confidence in yourself to attempt things which Isabella does not think difficult." Matilda shook her head--"I am not Isabella yet," said she. "No!" cried Isabella, with generous, sincere warmth; "but you are much superior to Isabella: I am certain that I could not answer those difficult questions, though you think me so quick--and, when once you have learned any thing, you never forget it; the ideas are not superficial," continued Isabella, turning to Mad. de Rosier; "they have depth, like the pins in mosaic work."