ATM quotes from Annals of Science, circa 1853

["Mel Bartels" <mbartels@efn.org>]

Annals of Science page 50

Among these peculiar revelations is that of the spiral form--the most
striking and appreciable of all--which we may venture to designate "The
Rossean Configuration."  Its discovery was at once novel and splendid;
and in reference to the dynamical principles on which these vast
aggregations of remote suns are whirled about within their respective
systems and sustained against interferences, promises to be of the
greatest importance.

One of the most splendid nebulae of this class--the great spiral or
whirlpool--has been figured in the Philosophical Transactions for 1850.
It may be considered as the grand type and example of a class; for near
40 more, with spiral characteristics, have been observed, and about 20
of them carefully figured.  Dr. Scoresby had the pleasure of being
present at the discovery of this particular form in a nebula of the
planetary denomination, in which two portions following spiral forms
were detected.  Its color was peculiar.--page blue.  He had the
privilege, too, of being present on another interesting occasion, when
the examination of the great nebula in Orion was first seen to yield
decisive tokens of resolution.
Annals of Science, page 188-189

Reflecting Telescopes.

For the further information of numerous amateurs who have busied
themselves with the construction of the reflecting telescope, we have
taken the following account of Lord Rosse's machine for grinding and
polishing large specula, from Holtzapffel on "Turning and Mechanical
Manipulation," Vol. III p. 1280.

With the view of avoiding the uncertainties of the hand-process, the
Earl of Rosse constructed a machine for grinding and polishing specula,"
...
"...Under these circumstances, the most accurate determination at which
I have been able to arrive is, that when the stroke of the second
eccentric 'G", is such as to communicate a lateral motion to the
polisher equal to about .27 of the diameter of the speculum, the curve
will be nearly parabolic."  The figure of the speculum is tested during
the grinding and polishing, by observing the reflection of the
watch-dial, and the adjustment of the length of stroke admits of being
made with such accuracy, that the three feet speculum "with its whole
aperture, is thrown perceptibly out of focus by a motion of the
eye-piece, amounting to less than the thirtieth of an inch; and even
with a single lens of an eighth of an inch focus, giving a power of
2592, the dots on a watch-dial are still in some degree defined."
...
There was still a difficulty with respect to the hardness of the
resinous composition' on the one hand it is essential to the truth of
the general figure that the composition should be soft enough to expand
laterally to enable it to fit the speculum, on the other hand the
composition is required to be as hard as is consistent with the
polishing powder being able to embed itself in its surface, in order
that the face of the speculum may be equally acted upon by the polisher,
notwithstanding minute differences in the texture of the metal at
different parts.  The Earl of Rosse found that the two properties
apparently inconsistent with each other, could be imparted to the
polisher at the same time, simply by using the resinous composition of
two degrees of hardness, so as to form two very thin strata, the outer
one being the harder.

Annals of Science page 51

In speaking of the effects of the flood of light accumulated by the
six-feet speculum of the Earl of Rosse, Dr. Scoresby remarked, that this
peculiarity of the instrument (connected as it is with due length of
focus and admirable definition,) enabled it to reach distances in space
far beyond the powers of any other instrument.  This was its peculiar
province; and in this, as to existing instruments, there was not, nor,
as he hoped to shew, could there be, any competition.  For comparing the
space-penetrating power of the six-feet speculum with one or two feet,
(which, has rarely been exceeded) we find it three to one in favor of
the largest, with an accumulation of light in the ratio of 6^2 to 2^3 or
9 to 1.  On comparing the powers of this magnificent instrument with
those of a refractor of two feet aperture, the largest hitherto
attempted, we have a superiority--making a due allowance for the loss of
light by reflection from two mirrors, and assuming an equal degree of
perfectness, figure, and other optical requirements in the refractor,
and no allowance for absorption of light--in the ratio of about 4.5 to
1, as to light, and as ?.12 to 1, as to the capability of penetrating
space, or detecting nebulous or sidereal objects at the extreme distance
of visibility.

Annals of Science

Composition for Silvering Glass
by Hale Thompson and Robert Mellish

Prepare a mixture of 30 grains ammonia, 60 grains nitrate of silver, 90
grains spirit of wine, and 90 grains of water.  When the nitrate of
silver is completely dissolved, filter the liquid and add a small
quantity of sugar, for example, 15 grains of the grape sugar previously
dissolved in a mixture of 1 1/2 ounces of water, and 1 1/2 ounces spirit
of wind.

For silvering a glass it is sufficient to leave this solution in contact
with the glass during two or three days. --Civil Engineers and
Architects Journal

Clear skies, Mel Bartels
http://www.efn.org/~mbartels