PETERSBURG. 
13 
to obtain the theory, and to ascertain the laws, chap. 
from which this structure results 1 2 3 . Monge, ' — ' 
President of the National Institute of Paris, 
noticed, in falling snow, stars with six equal 
rays, descending, during winter, when the 
atmosphere was calm. Hauy records this, in 
his observations on the muriate of ammonia *. 
The first droshy ’ had made its appearance in 
the streets of Petersburg before we left it ; and 
we began to entertain serious apprehensions 
that the snow would fail, and our sledge-way to 
Moscow be destroyed. We had often been told 
of the rapidity with which the warm season 
makes it appearance in this climate ; there being 
(1) An equiangular and equilateral plane hexagon is divisible into 
three equal and similar rhombs : and if the engraved Figure A ba 
attentively observed, it will appear that each linear ray of the star is 
a diagonal (See Figure B) , joining the acute angles of a rhomb, whose 
sides are the loci of the extreme points of the lines of ramification 
from those diagonals. The rhomb may therefore be the primitive 
form of water crystallized. This seems the more manifest, because 
if equal and similar rhombs be applied between all the rays of the 
star A, in the spaces 1, 2, 3, 4, 5, and 6, an equilateral and equi- 
angular hexagon will be the result ; as represented by the dotted line 
in Figure C. 
(2) “ II en r&ultc des etoiles a six rayons, lorsque 1c temps est 
ealme, et que la temperature n’est pas assez dlevea pour desformer les 
cristaux.” Hauy, Traitc dc Min. tom. ii. p. 386. 
(3) The droshy is a kind of bench upon four wheels, used in Russia 
as our Hackney-coaches : it contains four or six persons, sitting back to 
back, thus driven sideways by the coachman, who sits at the end of the 
bench. This vehicle succeed? the sledge, after the melting of the snow. 
