their Branches near alike, but others were more extended towards one Side. None, how-
ever, had any regular Position in respect of one another, or of the Sides of the Vessel ;
nor did any of them extend exactly every Way from the Center a.
It is necessary, in the Freezing of Urine for this Experiment, that its Superficies be not
disturbed by Wind, or any other Way ; and that it be not frozen too deep, for then the
branched Appearance becomes loft.
If the Inside of a smooth and clear Glass be wetted with Urine, and exposed in a sharp
Frost, it will be covered with very regular and curious Figures. But an artificial Freezing
with Snow and Salt, produces not the natural Shootings in Urine, unless the Quantity in
the Vessel be very small.
It is remarkable, that no urinous Taste was perceived in several clear Pieces of such
Ice, but they secmed as insipid as Water.
Somewhat like this Configuration of frozen Urine, tho' in some Particulars much more
curious, is observable in the Regulus Martis Stellatus ; but whereas in this Ice the Stems
and Branchings are all strait, in the Regulus they appear regularly bent or wreathed, in a
very beautiful Manner. Lead and Arsenic, with some other Mixtures, are also found to
have their Surface, when suffered to cool, with Branches not much unlike to those of
Urine, but smaller a great deal.
Dr. HOOKE takes occasion here to shew the Resemblance of the Shootings before de-
scribed,
in Urine, to the Branchings in the Leaves of Fern, whose Form, he says, is the
most simple and uncompounded of any Vegetable, except Mould or Mushrooms : For
the main Stem in Fern may be observed to send forth lateral Branches, from whence col-
lateral ones arise, and from them again sub-collateral ones, after much the same Order as
the Branchings, Divisions and Subdivisions appear in the Figures of frozen Urine. He adds,
that if both be well considered, there seems not much greater Need of a seminal Prin-
ciple to produce Fern, than for the Production of such Forms in Urine, or in the above-
mentioned Regulus Martis ; since as much Beauty and Regularity appears in the one as in
the other. And to this he subjoins, that notwithstanding several have affirmed that
Fern produces, and is propagated by Seed, he could never find any Part of it to be more
seminal than another, tho' he had made very diligent Enquiry as to that Particular.
'Tis a little surprizing that our Author was not able, with his Microscope, to discover
the Seeds of this Plant,
which produces them in the greatest Abundance on the Backs of
almost all its Leaves, in Seed-Vessels that appear to the naked Eye only like a black or
brown Scurf ; but, when viewed by the Microscope, resemble little circular Tubes di-
vided into many Cells, containing Seeds extremely minute. When the Seed is ripe, the
Vessels fly open with a Spring, and squirt the Seeds out on every Side, in the Form of
Dust : And if at that Season some of the Leaves are put into a Paper-Cone, and that be
held to the Ear, the Seed-Vessels may be heard to burst with a considerable Noise. Some
of these minute Vessels contain at least an hundred Seeds, invisible to the naked Eye.
One may reasonably believe our Author never looked for them on the Backs of the
Leaves ; but finding neither Flowers nor Seeds in the same manner as in other Plants, he
concluded too hastily that it produced neither. Such Mistakes in great Men afford us
useful Lessons of being very cautions in giving our Opinions, and never to determine be-
fore we have examined fully.
PLATE V. FIG. 2.
The Forms of Falling Snow
THE Works of Nature are no less admirable for their Variety than their Beauty !
Even in such Things as appear the most alike, a strict Examination will discover
to us Differences beyond all human Conception ! No two Grains of Sand are exactly
similar ! Nay, the very flakes of Snow afford an amazing Variety of Configuration,
Beauty and Size, though not one in a Thousand of those that see them fall, either know
or imagine any thing worth observing in them.
But Dr. HOOKE tells us, that catching the salling Snow on a black Hat, or a Piece of
black Cloth, he observed the curious Figures of its Flakes with the utmost Pleasure ; and
he presents us, out of a great Variety, with the several beautiful Forms under our Eye at
present.
Every Flake consists of six principal Branches or Stems, all of equal Length, Shape,
and Make, issuing from a Center ; and each of them inclining to the next on either Side
it in an Angle of sixty Degrees.
