PLATE IV. FIG. 2.
The Forms of Gravel in Urine
THE Sand or Gravel of Urine seems to be a tartarcous Substance, generated of saline
and carthy Matter chrystalized together,
sticking sometimes to the Sides of the
Chamber-Pot, but more frequently sinking to the Bottom, and there appearing in the Form
of coarse Sand ; the Grains whereof, seen through the Microscope, resemble a Company
of small Bodies, partly transparent, and partly opake ; some white, some yellow, some
red, and others of more brown and dusky Colours.
In Shape they are mostly flat, after the Manner of Slates, or such-like plated Stones ;
and seem composed of several very thin Lamellæ, like Muscovy Glass or Englisb Spar ; the
latter of which they appear nearly to resemble, having their Sides, as that has, form'd into
Rhombs, or Rhomboids, and sometimes into Rectangles and Squares.
The Figure under our Eye represents a Dozen of them, (as examined by the Micro-
scope, lying on a Slip of Glass, A B C D ; some whereof, as a, b, c, d, were more regu-
lar than the rest ; and e, a small one, sticking upon another, was a persect Rhomboid on
the Top, and had four rectangular Sides.
Their Bigness is shewn by the Line E, which was the Measure of the Microscope, and
a Scale of the thirty-second Part of an Inch magnified ; by this Measure it is evident,
that none of them exceeded in Breadth, the one hundred and twenty-eighth Part of an
Inch.
Oil of Vitriol, Spirit of Urine, and several saline Menstrua, diffolved them in a Minute or
two without any Ebullition : Water and many other Liquors had no sudden Effect upon
them. Such Fluids as diffolve them, render them very white at first, not spoiling but ra-
ther rectifying their Figures, and making them more agreeable Objects for the Microscope.
PLATE IV. FIG. 3, and 4.
A Variety of regular Forms resulting from various Combinations of
Globules
DR. HOOKE imagines the Chrystalization of Salts, and all those regular Figures that
are so remarkably various and curious,
| Effocts of a Combination of Globules. |
and beautify such Multitudes of Bodies, arise
only from three or four different Positions of globular Particles ; and those the most plain,
obvious, and necessary Conjunctions of such figured Particles that can possibly happen. So
that, supposing such plain and obvious Causes concurring, the coagulating Particles must,
as necessarily, compose a Body of such a determinate regular Figure, and no other, as a
fluid Body encompassed with an heterogeneous Fluid must be rounded into a Globule or
Sphere. And he says, he has demonstrated, only by a Company of Bullets, and one or
two other very simple Bodies, that merely almost by shaking them together, he could
make them compose any regular Figure he had ever met with.
For Example : If a Number of Bullets be put on an inclining Plane, so that they may
run together, they will fall, naturally, into a triangular Order, composing all the Variety
of Figures that can be imagined to be made out of æquilateral Triangles ; such as all the
Surfaces of Alum, upon Examination, will be found to be ; for three Bullets lying on a
Plane, as close as they can to one another, compose an æquilateral-triangular Form, as is
shewn at A.
If a Fourth be joined to them, as closely as it can, on either Side, the four together
form a most regular Rhombus, consisting of two æquilateral Triangles, as B.
If a Fifth be joined to them on either Side, in as close a Position as can be, (which is a
Circumstance always to be understood in these Experiments) it makes a Trapezium, or
four-sid?d Figure, two of whose Angles are 120, and the other two 60 Degrees,
as C.
On the Addition of a Sixth, as before, it makes either an æquilateral Triangle, like
D ; or a Rbomboid, as E ; or an bexangular Figure composed of two primary Rbombes,
as F.
If we add a Seventh, it makes either an æquilatero-bexagonal Figure, as G ; or some
kind of six-sided Figure, like H, or I.
And though never so many be placed together, they may be all ranged under some of
these before mentioned Forms, with Angles either of sixty, or one hundred and twenty
