next year in the oratorios, I had, for a
whole twelvemonth, two lessons per week from Miss Fleming, the
celebrated dancing-mistress, to drill me for a gentlewoman (God
knows how she succeeded). So we lived on without interruption. My
brother Alex. was absent from Bath for some months every summer,
but when at home he took much pleasure in executing some turning or
clockmaker's work for his brother."

The music, and the astronomy, and the making of telescopes, all went on
together, each at high pressure, and enough done in each to satisfy any
ordinary activity. But the Herschels knew no rest. Grinding mirrors by
day, concerts and oratorios in the evening, star-gazing at night. It is
strange his health could stand it.

The star-gazing, moreover, was no _dilettante_ work; it was based on a
serious system--a well thought out plan of observation. It was nothing
less than this--to pass the whole heavens steadily and in order through
the telescope, noting and describing and recording every object that
should be visible, whether previously known or unknown. The operation is
called sweeping; but it is not a rapid passage from one object to
another, as the term might suggest; it is a most tedious business, and
consists in following with the telescope a certain field of view for
some minutes, so as to be sure that nothing is missed, then shifting it
to the next overlapping field, and watching again. And whatever object
appears must be scrutinized anxiously to see what there is peculiar
about it. If a star, it may be double, or it may be coloured, or it may
be nebulous; or again it may be variable, and so its brightness must be
estimated in order to compare with a subsequent observation.

Four distinct times in his life did Herschel thus pass the whole visible
heavens under review; and each survey occupied him several years. He
discovered double stars, variable stars, nebulae, and comets; and Mr.
William Herschel, of Bath, the amateur astronomer, was gradually
emerging from his obscurity, and becoming a known man.

Tuesday, the 13th of March, 1781, is a date memorable in the annals of
astronomy. "On this night," he writes to the Royal Society, "in
examining the small stars near _[eta]_ Geminorum, I perceived one
visibly larger than the rest. Struck with its uncommon appearance, I
compared it to _[eta]_ Geminorum and another star, and finding it so
much larger than either, I suspected it to be a com