search after perfection, the same nice ingenuity of means; and
though the holophotal revolving light perhaps still remains his most
elegant contrivance, it is difficult to give it the palm over the much
later condensing system, with its thousand possible modifications. The
number and the value of these improvements entitle their author to the
name of one of mankind's benefactors. In all parts of the world a safer
landfall awaits the mariner. Two things must be said: and, first, that
Thomas Stevenson was no mathematician. Natural shrewdness, a sentiment
of optical laws, and a great intensity of consideration, led him to just
conclusions; but to calculate the necessary formulae for the instruments
he had conceived was often beyond him, and he must fall back on the help
of others, notably on that of his cousin and lifelong intimate friend,
_emeritus_ Professor Swan,[7] of St. Andrews, and his later friend,
Professor P. G. Tait. It is a curious enough circumstance, and a great
encouragement to others, that a man so ill equipped should have
succeeded in one of the most abstract and arduous walks of applied
science. The second remark is one that applies to the whole family, and
only particularly to Thomas Stevenson from the great number and
importance of his inventions: holding as the Stevensons did a Government
appointment, they regarded their original work as something due already
to the nation, and none of them has ever taken out a patent. It is
another cause of the comparative obscurity of the name; for a patent not
only brings in money, it infallibly spreads reputation; and my father's
instruments enter anonymously into a hundred light-rooms, and are passed
anonymously over in a hundred reports, where the least considerable
patent would stand out and tell its author's story.

But the life-work of Thomas Stevenson remains; what we have lost, what
we now rather try to recall, is the friend and companion. He was a man
of a somewhat antique strain: with a blended sternness and softness that
was wholly Scottish, and at first somewhat bewildering; with a profound
essential melancholy of disposition and (what often accompanies it) the
most humorous geniality in company; shrewd and childish; passionately
attached, passionately prejudiced; a man of many extremes, many faults
of temper, and no very stable foothold for himself among life's
troubles. Yet he was a wise adviser; many men, and these not
inconsiderable, took counsel with