of _Saturn_, I discovered a _sixth_ satellite of that planet, and
also saw the spots upon _Saturn_ better than I had ever seen them
before, so that I may date the finishing of the forty-foot telescope
from that time."

Another satellite of _Saturn_ was discovered with the forty-foot on the
17th of September (1789). It was used for various observations so late
as 1811. On January 19, of that year, HERSCHEL observed the nebula of
_Orion_ with it. This was one of his last observations.

The final disposition of the telescope is told in the following extract
from a letter of Sir JOHN HERSCHEL'S to Mr. WELD, Secretary of the Royal
Society:

"COLLINGWOOD, _March 13, 1847_.

. . . "In reply to your queries, respecting the forty-foot
reflecting telescope constructed by my father, I have to state that
King GEORGE III. munificently defrayed the _entire_ cost of that
instrument (including, of course, all preparatory cost in the nature
of construction of tools, and of the apparatus for casting, grinding,
and figuring the reflectors, of which two were constructed), at a
total cost of L4,000. The woodwork of the telescope being so far
decayed as to be dangerous, in the year 1839 I pulled it down, and
piers were erected on which the tube was placed, _that_ being of
iron and so well preserved, that, although not more than
one-twentieth of an inch thick, when in the horizontal position it
sustained within it all my family, and continues to sustain inclosed
within it, to this day, not only the heavier of the two reflectors,
but also all the more important portions of the machinery. . . .
The mirror and the rest of the polishing apparatus are on the
premises. The iron grinding tools and polishers are placed
underneath the tube, let into the ground, and level with the surface
of the gravelled area in which it stands.". . .

The closing of the tube was done with appropriate ceremony on
New-Year's-Day, 1840, when, after a procession through it by the family
at Slough, a poem, written by Sir JOHN, was read, the machinery put into
its present position, and the tube sealed.

The memoir on the forty-foot telescope shows throughout that HERSCHEL'S
prime object was not the making of the telescope itself, but that his
mind was constantly directed towards the uses to which it was to be
put--towards the questions which he