One of the exquisite wonders of the sea is called 
the Opelet, and is about as large as ihe Oermau 
aster, looking, indeed, very 
So few 
provision is 
houses 
made 
are well ventilated that, unless 
for this in any given case, there 
much like one. Imagine a 
very large double aster, with 
ever so many long petals of 
light green, glossy satin, and 
each one tipped with rose- 
color. These lovely petals 
do not lie quietly in their 
places, like those of the as¬ 
ter in your garden, hut wave 
about in the water, while the 
Opelet clings to a rock. 
How innocent and lovely it 
looks on its rocky bed! 
Who would suspect that it 
would eat anything grosser 
But 
those beautiful waving arms, 
as you call them, have an¬ 
other use besides 
pretty. They have to pro¬ 
vide food for a large open 
mouth, which is hidden deep 
down amongst them — so 
well hidden that one can 
scarcely find it. Well do 
they perform their duty, for 
the instant a foolish little 
fish touches one of the rosy 
tips lie is struck with poison, 
stove-pipe or chimney, if it he in cold weather. Take 
out a pane ol glass from the upper window, place 
a, pane of tin instead. Through the centre of this 
cut a hole say four inches in diameter, and onto this, 
in the room side of it, sol¬ 
der a tin elbow, with joint 
eight inches into the room 
and one loot and a half in 
length for the turn-up. 
Into the horizontal part in¬ 
sert a damper such as is 
put into stove-pipes, and 
you have ns good a venti¬ 
lator as one could ask. — 
Laws of Life. 
HEIGHT OP TREES. 
When a tree stands so 
that the length of its sha¬ 
dow' can be measured, its 
height can be readily as¬ 
certained as follows: Set 
a stick upright j let it be 
perpendicular by the 
plumb-line. Measure the 
length of the shadow of 
the tree, and at the same 
time measure the lenatli of 
O 
the shadow' of the stick. 
As the length of its sha¬ 
dow' is to the height of the 
stick, so is the length of the 
shadow of the tree to its 
height. For instance : If 
the stick is four feet above 
the ground and its shadow 
is six feet in length and 
the shadow of the tree is 
ninety feet, the height of 
the tree will be sixty feet 
(6:4::90:60). In other words, 
multiply the length of the 
shadow of the tree by the height of the stick, and 
divide by the shadow of the stick. 
