increasing optical power has enlarged the list of clusters, by
diminishing that of the nebulae properly so-called. Such has always
been the case since the nebulae have been observed with telescopes,
and although it would be unsafe to draw the inference, it is
impossible not to feel some expectation that with sufficient optical
power the nebulae would all be reduced into clusters. Perhaps the two
of the most remarkable of the resolved nebulae are Fig. 26 and Fig.
55. In several of the planetary nebulae we have discovered a star or
bright point in the centre, and a filamentous edge, which is just
the appearance which a cluster with a highly condensed centre would
present in a small instrument. For instance, Figs. 47 and 32. We
have also found that many of the nebulae have not a symmetrical form,
as they appear to have in inferior instruments; for instance, Fig.
81 is a cluster with long resolvable filaments from its southern
extremity, and Fig. 85 is an oblong cluster with a bright centre.
Fig. 45 is an annular nebula, like Herschel's drawing of the annular
nebula in Lyra. I have sent drawings of a few of these objects to
the Royal Society, they were forwarded a few days ago. We have upon
the whole as yet observed but little with the telescope of 3 feet
aperture. You recollect Herschel said that it was a good observing
year, in which there were 100 hours fit for observing, and of the
average of our hours I have not employed above 30. We have been for
the last two years engaged in constructing a telescope of 6 feet
aperture and 52 feet focus, and it would have been impossible to
have bestowed the necessary attention upon it had we made a business
of observing. That instrument is nearly finished, and I hope it will
effect something for astronomy. The unequal refraction of the
atmosphere will limit its powers, but how far remains to be
ascertained.... Lady Rosse joins me in very kind remembrances and
believe me to be,

Dear Mrs. Somerville,
Yours very truly and ever,
ROSSE.

* * * * *

[Sir John Herschel wrote to my father from the Cape:--]

FROM SIR JOHN HERSCHEL TO MR. SOMERVILLE.

FELDHAUSEN, NEAR WYNBERG, C.G.H., _July 17th, 1830_.