66 THE YOUNG 
fining fish, where the water remains un- 
changed and at rest, the water should be 
spread over as great a surface as possible, 
and at the same time should present a 
reasonable depth for the perfect display 
of the animals. 
In the case of the glass jar, surrounded 
on all sides with light, the water becomes 
warmer than that in the wash basin, and 
as a consequence it is in a condition to 
take up less oxygen. Fish placed in ves- 
sels composed entirely of glass, become 
greatly woried and excited for the first few 
hours, caused by glare of light on all 
sides, in their vain attempts to pass 
through the glass and thus make their 
escape; and then, again, they are under 
constant alarm, caused by the moving ob- 
jects that surround them. Under these 
exciting conditions they breathe much 
faster, and consequently exhaust the 
oxygen more rapidly than when in a 
natural condition. 
I know a scientific gentleman who some 
years ago kept a fresh- water crayfish for 
over two years. It must be remembered 
that this crustacean is considered by 
dealers to be one of the most difficult 
animals to keep in stock. The secret of 
his success was entirely due to the shal- 
lowness of the water in which the crayfish 
was kept. I will quote his own words: 
I have succeeded in keeping a cray- 
fish for over two years, which I have kept 
in water not more than an inch and a half 
deep, previous experiments having shown 
that in deeper water these animals always 
died in course of time for want of sufficient 
aeration. His appetite during the two 
years was always good. lUe water was 
never changed, but some was occasionally 
added to supply the loss by evaporation. 
Had this crayfish not met with an acci- 
dent it might have lived many years 
longer." 
I had, on one occasion, a number of 
dace live and do well in a long tank where 
the water was shallow, and stood during 
the day at a temperature of 78° Fahr. 
It is well to remember that air dissolved 
by water is always richer in oxygen than 
the atmosphere breathed by terrestrial 
animals. One-third of the air absorbed 
by water consists of oxygen, instead of 
only one-fifth, as is present in the atmos- 
phere. 
SCIENTIST. 
A Hanging Bird House. 
THE bird house represented in this fig- 
ure is constructed out of a combina- 
tion of flower pots and old milk pans, ar- 
ranged so as to resemble, in form (when 
coated with plaster of Paris), an acorn. 
The top consists of a five-inch flower pot 
inverted, which has the bottom cut out. 
This pot is fastened to an old milk pan ; 
this pan is fastened to a larger-sized pan, 
the rim of which extends over a 14-inch 
flower pot. The small flower pot and the 
tin pans are to represent the cup of the 
acorn, when coated with plaster of Paris. 
The 14:-inch pot is to represent ^he nut of 
HANGING BIKD HOUSE. 
the acorn. Both pans are punched full of 
holes, so that when the plaster is laid on 
it will pass into the holes and clinch, 
otherwise it will not adhere to the smooth 
surface of the tin. Holes are made in the 
bottoms of the pans and the large pot, 
for a turned picket or stick to pass 
through ; at the bottom of the large pot a 
hole is bored through the picket into 
which a pin of iron or wood is inserted to 
prevent the pots and pans from slipping 
off. In applying the plaster to the pot I 
