THE TANK. 



23 



or what is known in the seed-stores as a " propagating 

 glass." An article of this kind is inverted, and the knob 

 at the bottom set in a wooden stand of mahogany, or 

 oak, or pine, to suit the taste or other views of the pro- 

 prietor. A common fish-globe has been converted into a 

 tank for an Aquarium with very little difficulty. 



Constructed entirely of glass, all these substitutes for a 

 regularly prepared tank permit their contents to be 

 inspected with facility, but they are all alike obnoxious to 

 two fatal objections. One of them we have alluded to as 

 an unequal refraction, which distorts and deforms every 

 object placed in the water, and subjects them to a change 

 of shape and magnitude, while in motion, at every 

 moment. The other may be found in the fact that, 

 if manufactured of any size worth consideration, they will 

 not stand the pressure of the water, and are liable at the 

 shghtest touch to burst into fragments, scattering a col- 

 lection the, result perhaps of patient study and compari- 

 son, as well as of some outlay in time, and money, and 

 affection, over the carpeted floor. The vibration pro- 

 duced by an approaching footstep, we have known to 

 occasion such a calamity, long after all reason for appre- 

 hension seemed to have passed away. In truth, glass 

 tanks of a spherical or cylindrical form are not to be 

 depended upon in any respect. They are never perfect. 

 Their mode of manufacture renders them, of necessity, 

 frail ; and it is a poor economy that will hazard, to save 

 the expense of a suitable and permanent tank, all the 



