CENTENNIAL EXPOSITION AT CINCINNATI. 
877 
nsiderable difficulty was met with in arranging the live-fish display, 
in accordance with the plan for this part of the exhibit a structure 
representing a section of a rocky sloping hillside was erected for the 
reception of the aquaria, a row of which was arranged around the front, 
while two rows were placed on either side of a grotto-like passageway (6 
feet wide) that ran from end to end beneath the hill. There were twenty- 
one tanks in all thus located, besides which two larger tanks were 
placed on trestles on each side of the main avenue connecting the Smith- 
sonian and National Museum exhibit with that of the Fish Commission. 
In the center of the hill a tiny rivulet tumbled down the steep and 
broken declivity, fell into a basin below, and thence passed through a 
McDonald fishway (or ladder) to a miniature pond on the floor. 
It will readily be understood that, even under the most favorable 
conditions imaginable, the erection of such a structure, the installation 
of aquaria, the building of a miniature pond, the preparation for light- 
ing the aquaria by electricity, and the arrangements for filtering and 
regulating the temperature of the water required much labor and special 
skill. The building of the structure was, however, pushed forward with 
all possible diligence. A double force was employed, one gang working 
during the day and the other at night. On account of the nature of the 
mateiials used in making the imitation rock- work, considerable time was 
consumed in getting the grotto into shape to admit visitors. It was 
completed in the latter part of July. The chief difficulty, however, lay 
in obtaining a sufficient supply of filtered water. The excessively muddy 
condition of the water made it imperative to filter all that was used, and 
the supply needed was large, since a continuous circulation had to be 
kept up to maintain the fish in a healthy condition.* 
The most efficient method of obtaining a water supply and proper 
aeration of aquaria is that of having a very small stream delivered 
with strong pressure, and which, penetrating the surface of the water in 
the tanks, carries in with it a large amount of air that is dispersed in 
minute bubbles. The method of filtration must be adapted to this 
purpose. Certain unexpected obstacles were developed before the de- 
tails were finally and satisfactorily completed, which not only delayed 
the work, but for a time appeared to make a successful exhibit of live 
fish impossible. 
The pressure of water from the city mains at Cincinnati is very great, 
ranging from 60 to 75 pounds to the square inch. The chief difficulty, 
however, was due to an elevator run by hydraulic power, located not 
far from the Fish Commission exhibit, the operations of which caused 
excessive and rapid fluctuations of pressure, varying in an instant from 
* There were 53 rainy days during the exposition period, and the Ohio River, usu- 
ally low and comparatively clear during summer, was very high and phenomeually 
muddy during all this time. Nevertheless, after the conditions were fully understood 
and means found to control them, it was practicable to provide water of perfect 
clearness and brilliance. 
