The mirror of the telescope is 8 inches in diameter;
its focal length, 5 feet; and the tube in which it is mounted,
about 6 feet long. The instrument seemed to me to have an
excellent defining power.
But Mr. Lancaster, like every eager astronomer, is anxious for
further improvements. He considers the achromatic telescope the
king of instruments, and is now engaged in testing convex optical
surfaces, with a view to achieving a telescope of that
description. The chief difficulty is the heavy charge for the
circular blocks of flint glass requisite for the work which he
meditates. "That," he says, "is the great difficulty with
amateurs of my class." He has, however, already contrived and
constructed a machine for grinding and polishing the lenses in an
accurate convex form, and it works quite satisfactorily. Mr.
Lancaster makes his own tools. From the raw material, whether of
glass or steel, he produces the work required. As to tools, all
that he requires is a bar of steel and fire; his fertile brain
and busy hands do the rest. I looked into the little workshop
behind his sitting-room, and found it full of ingenious
adaptations. The turning lathe occupies a considerable part of
it; but when he requires more space, the village smith with his
stithy, and the miller with his water-power, are always ready to
help him. His tools, though not showy, are effective.
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