"Still, with all the school-masters, and all the teaching, and all the books, the ignorance of the unscientific world is enormous; they are ignorant both ways--they underrate the scientific people and they overrate them. There is, on the one hand, the Irish woman who is disappointed because you cannot tell fortunes, and, on the other hand, the cultivated woman who supposes that you must know _all_ science. "I have a friend who wonders that I do not take my astronomical clock to pieces. She supposes that because I am an astronomer, I must be able to be a clock-maker, while I do not handle a tool if I can help it! She did not expect to take her piano to pieces because she was musical! She was as careful not to tinker it as I was not to tinker the clock, which only an expert in clock-making was prepared to handle. "... Only a few weeks since I received a letter from a lady who wished to come to make me a visit, and to 'scan the heavens,' as she termed it. Now, just as she wrote, the clock, which I was careful not to meddle with, had been rapidly gaining time, and I was standing before it, watching it from hour to hour, and slightly changing its rate by dropping small weights upon its pendulum. Time is so important an element with the astronomer, that all else is subordinate to it. "Then, too, the uneducated assume the unvarying exactness of mathematical results; while, in reality, mathematical results are often only approximations. We say the sun is 91,000,000 miles from the earth, plus or minus a probable error; that is, we are right, probably, within, say, 100,000 miles; or, the sun is 91,000,000 minus 100,000 miles, or it is 91,000,000 plus 100,000 miles off; and this probable error is only a probability. "If we make one more observation it cannot agree with any one of our determinations, and it changes our probable error. [Illustration: BUST OF MARIA MITCHELL. _From Original made by Miss Emma F. Brigham in 1877_] "This ignorance of the masses leads to a misconception in two ways; the little that a scientist can do, they do not understand,--they suppose him to be godlike in his capacity, and they do not see results; they overrate him and they underrate him--they underrate his work. "There is no observatory in this land, nor in any land, probably, of which the question is not asked, 'Are they doing anything? Why don't we hear from them? They should make discoveries, they should publish.' "The one observation made at Greenwich on the planet Neptune was not published until after a century or more--it was recorded as a star. The observation had to wait a hundred years, about, before the time had come when that evening's work should bear fruit; but it was good, faithful work, and its time came. "Kepler was years in passing from one of his laws to another, while the school-boy, to-day, rattles off the three as if they were born of one breath.